diff --git a/accessible/generic/Accessible.cpp b/accessible/generic/Accessible.cpp
index 90824577e5d5..62df58716e85 100644
--- a/accessible/generic/Accessible.cpp
+++ b/accessible/generic/Accessible.cpp
@@ -317,10 +317,9 @@ Accessible::TranslateString(const nsString& aKey, nsAString& aStringOut)
   if (!stringBundle)
     return;
 
-  nsXPIDLString xsValue;
+  nsAutoString xsValue;
   nsresult rv =
-    stringBundle->GetStringFromName(NS_ConvertUTF16toUTF8(aKey).get(),
-                                    getter_Copies(xsValue));
+    stringBundle->GetStringFromName(NS_ConvertUTF16toUTF8(aKey).get(), xsValue);
   if (NS_SUCCEEDED(rv))
     aStringOut.Assign(xsValue);
 }
@@ -2835,37 +2834,32 @@ KeyBinding::ToPlatformFormat(nsAString& aValue) const
     return;
 
   nsAutoString separator;
-  keyStringBundle->GetStringFromName("MODIFIER_SEPARATOR",
-                                     getter_Copies(separator));
+  keyStringBundle->GetStringFromName("MODIFIER_SEPARATOR", separator);
 
   nsAutoString modifierName;
   if (mModifierMask & kControl) {
-    keyStringBundle->GetStringFromName("VK_CONTROL",
-                                       getter_Copies(modifierName));
+    keyStringBundle->GetStringFromName("VK_CONTROL", modifierName);
 
     aValue.Append(modifierName);
     aValue.Append(separator);
   }
 
   if (mModifierMask & kAlt) {
-    keyStringBundle->GetStringFromName("VK_ALT",
-                                       getter_Copies(modifierName));
+    keyStringBundle->GetStringFromName("VK_ALT", modifierName);
 
     aValue.Append(modifierName);
     aValue.Append(separator);
   }
 
   if (mModifierMask & kShift) {
-    keyStringBundle->GetStringFromName("VK_SHIFT",
-                                       getter_Copies(modifierName));
+    keyStringBundle->GetStringFromName("VK_SHIFT", modifierName);
 
     aValue.Append(modifierName);
     aValue.Append(separator);
   }
 
   if (mModifierMask & kMeta) {
-    keyStringBundle->GetStringFromName("VK_META",
-                                       getter_Copies(modifierName));
+    keyStringBundle->GetStringFromName("VK_META", modifierName);
 
     aValue.Append(modifierName);
     aValue.Append(separator);
diff --git a/accessible/generic/ApplicationAccessible.cpp b/accessible/generic/ApplicationAccessible.cpp
index 6679944d6f2c..6bb69fbb272a 100644
--- a/accessible/generic/ApplicationAccessible.cpp
+++ b/accessible/generic/ApplicationAccessible.cpp
@@ -53,8 +53,8 @@ ApplicationAccessible::Name(nsString& aName)
   if (NS_FAILED(rv))
     return eNameOK;
 
-  nsXPIDLString appName;
-  rv = bundle->GetStringFromName("brandShortName", getter_Copies(appName));
+  nsAutoString appName;
+  rv = bundle->GetStringFromName("brandShortName", appName);
   if (NS_FAILED(rv) || appName.IsEmpty()) {
     NS_WARNING("brandShortName not found, using default app name");
     appName.AssignLiteral("Gecko based application");
diff --git a/browser/components/shell/nsGNOMEShellService.cpp b/browser/components/shell/nsGNOMEShellService.cpp
index 5ebeb5e66a87..8c710798dbcc 100644
--- a/browser/components/shell/nsGNOMEShellService.cpp
+++ b/browser/components/shell/nsGNOMEShellService.cpp
@@ -288,9 +288,8 @@ nsGNOMEShellService::SetDefaultBrowser(bool aClaimAllTypes,
     rv = bundleService->CreateBundle(BRAND_PROPERTIES, getter_AddRefs(brandBundle));
     NS_ENSURE_SUCCESS(rv, rv);
 
-    nsString brandShortName;
-    brandBundle->GetStringFromName("brandShortName",
-                                   getter_Copies(brandShortName));
+    nsAutoString brandShortName;
+    brandBundle->GetStringFromName("brandShortName", brandShortName);
 
     // use brandShortName as the application id.
     NS_ConvertUTF16toUTF8 id(brandShortName);
@@ -399,7 +398,7 @@ nsGNOMEShellService::SetDesktopBackground(nsIDOMElement* aElement,
   nsAutoCString filePath(PR_GetEnv("HOME"));
 
   // get the product brand name from localized strings
-  nsString brandName;
+  nsAutoString brandName;
   nsCID bundleCID = NS_STRINGBUNDLESERVICE_CID;
   nsCOMPtr<nsIStringBundleService> bundleService(do_GetService(bundleCID));
   if (bundleService) {
@@ -407,8 +406,7 @@ nsGNOMEShellService::SetDesktopBackground(nsIDOMElement* aElement,
     rv = bundleService->CreateBundle(BRAND_PROPERTIES,
                                      getter_AddRefs(brandBundle));
     if (NS_SUCCEEDED(rv) && brandBundle) {
-      rv = brandBundle->GetStringFromName("brandShortName",
-                                          getter_Copies(brandName));
+      rv = brandBundle->GetStringFromName("brandShortName", brandName);
       NS_ENSURE_SUCCESS(rv, rv);
     }
   }
diff --git a/browser/components/shell/nsWindowsShellService.cpp b/browser/components/shell/nsWindowsShellService.cpp
index d38453075465..43cda7d80e89 100644
--- a/browser/components/shell/nsWindowsShellService.cpp
+++ b/browser/components/shell/nsWindowsShellService.cpp
@@ -614,10 +614,9 @@ nsWindowsShellService::SetDesktopBackground(nsIDOMElement* aElement,
   NS_ENSURE_SUCCESS(rv, rv);
 
   // e.g. "Desktop Background.bmp"
-  nsString fileLeafName;
-  rv = shellBundle->GetStringFromName
-                      ("desktopBackgroundLeafNameWin",
-                       getter_Copies(fileLeafName));
+  nsAutoString fileLeafName;
+  rv = shellBundle->GetStringFromName("desktopBackgroundLeafNameWin",
+                                      fileLeafName);
   NS_ENSURE_SUCCESS(rv, rv);
 
   // get the profile root directory
diff --git a/caps/nsScriptSecurityManager.cpp b/caps/nsScriptSecurityManager.cpp
index 90695ebd126f..db589560c9dd 100644
--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -1003,14 +1003,14 @@ nsScriptSecurityManager::CheckLoadURIFlags(nsIURI *aSourceURI,
                              &hasSubsumersFlag);
     NS_ENSURE_SUCCESS(rv, rv);
     if (!hasFlags && !hasSubsumersFlag) {
-        nsXPIDLString message;
+        nsAutoString message;
         NS_ConvertASCIItoUTF16 ucsTargetScheme(targetScheme);
         const char16_t* formatStrings[] = { ucsTargetScheme.get() };
         rv = sStrBundle->
             FormatStringFromName("ProtocolFlagError",
                                  formatStrings,
                                  ArrayLength(formatStrings),
-                                 getter_Copies(message));
+                                 message);
         if (NS_SUCCEEDED(rv)) {
             nsCOMPtr<nsIConsoleService> console(
               do_GetService("@mozilla.org/consoleservice;1"));
@@ -1041,14 +1041,14 @@ nsScriptSecurityManager::ReportError(JSContext* cx, const char* aMessageTag,
     NS_ENSURE_SUCCESS(rv, rv);
 
     // Localize the error message
-    nsXPIDLString message;
+    nsAutoString message;
     NS_ConvertASCIItoUTF16 ucsSourceSpec(sourceSpec);
     NS_ConvertASCIItoUTF16 ucsTargetSpec(targetSpec);
     const char16_t *formatStrings[] = { ucsSourceSpec.get(), ucsTargetSpec.get() };
     rv = sStrBundle->FormatStringFromName(aMessageTag,
                                           formatStrings,
                                           ArrayLength(formatStrings),
-                                          getter_Copies(message));
+                                          message);
     NS_ENSURE_SUCCESS(rv, rv);
 
     // If a JS context was passed in, set a JS exception.
@@ -1285,20 +1285,20 @@ nsScriptSecurityManager::CanCreateWrapper(JSContext *cx,
     NS_ConvertUTF8toUTF16 originUnicode(origin);
     NS_ConvertUTF8toUTF16 classInfoName(objClassInfo.GetName());
     nsresult rv;
-    nsXPIDLString errorMsg;
+    nsAutoString errorMsg;
     if (originUnicode.IsEmpty()) {
         const char16_t* formatStrings[] = { classInfoName.get() };
         rv = sStrBundle->FormatStringFromName("CreateWrapperDenied",
                                               formatStrings,
                                               1,
-                                              getter_Copies(errorMsg));
+                                              errorMsg);
     } else {
         const char16_t* formatStrings[] = { classInfoName.get(),
                                             originUnicode.get() };
         rv = sStrBundle->FormatStringFromName("CreateWrapperDeniedForOrigin",
                                               formatStrings,
                                               2,
-                                              getter_Copies(errorMsg));
+                                              errorMsg);
     }
     NS_ENSURE_SUCCESS(rv, rv);
 
diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index f5d9001191d8..a0b026fe53b8 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -5305,9 +5305,8 @@ nsDocShell::DisplayLoadError(nsresult aError, nsIURI* aURI,
     for (uint32_t i = 0; i < formatStrCount; i++) {
       strs[i] = formatStrs[i].get();
     }
-    nsXPIDLString str;
-    rv = stringBundle->FormatStringFromName(error, strs, formatStrCount,
-                                            getter_Copies(str));
+    nsAutoString str;
+    rv = stringBundle->FormatStringFromName(error, strs, formatStrCount, str);
     NS_ENSURE_SUCCESS(rv, rv);
     messageStr.Assign(str.get());
   }
@@ -13372,14 +13371,12 @@ nsDocShell::ConfirmRepost(bool* aRepost)
   NS_ASSERTION(prompter && brandBundle && appBundle,
                "Unable to set up repost prompter.");
 
-  nsXPIDLString brandName;
-  rv = brandBundle->GetStringFromName("brandShortName",
-                                      getter_Copies(brandName));
+  nsAutoString brandName;
+  rv = brandBundle->GetStringFromName("brandShortName", brandName);
 
-  nsXPIDLString msgString, button0Title;
+  nsAutoString msgString, button0Title;
   if (NS_FAILED(rv)) { // No brand, use the generic version.
-    rv = appBundle->GetStringFromName("confirmRepostPrompt",
-                                      getter_Copies(msgString));
+    rv = appBundle->GetStringFromName("confirmRepostPrompt", msgString);
   } else {
     // Brand available - if the app has an override file with formatting, the
     // app name will be included. Without an override, the prompt will look
@@ -13388,14 +13385,13 @@ nsDocShell::ConfirmRepost(bool* aRepost)
     rv = appBundle->FormatStringFromName("confirmRepostPrompt",
                                          formatStrings,
                                          ArrayLength(formatStrings),
-                                         getter_Copies(msgString));
+                                         msgString);
   }
   if (NS_FAILED(rv)) {
     return rv;
   }
 
-  rv = appBundle->GetStringFromName("resendButton.label",
-                                    getter_Copies(button0Title));
+  rv = appBundle->GetStringFromName("resendButton.label", button0Title);
   if (NS_FAILED(rv)) {
     return rv;
   }
diff --git a/dom/animation/AnimationPerformanceWarning.cpp b/dom/animation/AnimationPerformanceWarning.cpp
index d8917cee0147..e791845ea134 100644
--- a/dom/animation/AnimationPerformanceWarning.cpp
+++ b/dom/animation/AnimationPerformanceWarning.cpp
@@ -12,7 +12,7 @@ namespace mozilla {
 
 template<uint32_t N> nsresult
 AnimationPerformanceWarning::ToLocalizedStringWithIntParams(
-  const char* aKey, nsXPIDLString& aLocalizedString) const
+  const char* aKey, nsAString& aLocalizedString) const
 {
   nsAutoString strings[N];
   const char16_t* charParams[N];
@@ -28,7 +28,7 @@ AnimationPerformanceWarning::ToLocalizedStringWithIntParams(
 
 bool
 AnimationPerformanceWarning::ToLocalizedString(
-  nsXPIDLString& aLocalizedString) const
+  nsAString& aLocalizedString) const
 {
   const char* key = nullptr;
 
diff --git a/dom/animation/AnimationPerformanceWarning.h b/dom/animation/AnimationPerformanceWarning.h
index 63296ef69403..c0ee92cc89aa 100644
--- a/dom/animation/AnimationPerformanceWarning.h
+++ b/dom/animation/AnimationPerformanceWarning.h
@@ -12,7 +12,7 @@
 #include "mozilla/Maybe.h"
 #include "nsTArray.h"
 
-class nsXPIDLString;
+class nsAString;
 
 namespace mozilla {
 
@@ -62,10 +62,10 @@ struct AnimationPerformanceWarning
   // Optional parameters that may be used for localization.
   Maybe<nsTArray<int32_t>> mParams;
 
-  bool ToLocalizedString(nsXPIDLString& aLocalizedString) const;
+  bool ToLocalizedString(nsAString& aLocalizedString) const;
   template<uint32_t N>
   nsresult ToLocalizedStringWithIntParams(
-    const char* aKey, nsXPIDLString& aLocalizedString) const;
+    const char* aKey, nsAString& aLocalizedString) const;
 
   bool operator==(const AnimationPerformanceWarning& aOther) const
   {
diff --git a/dom/animation/KeyframeEffectReadOnly.cpp b/dom/animation/KeyframeEffectReadOnly.cpp
index d7289bf12978..692c999be3a6 100644
--- a/dom/animation/KeyframeEffectReadOnly.cpp
+++ b/dom/animation/KeyframeEffectReadOnly.cpp
@@ -1139,7 +1139,7 @@ KeyframeEffectReadOnly::GetProperties(
       NS_ConvertASCIItoUTF16(nsCSSProps::GetStringValue(property.mProperty));
     propertyDetails.mRunningOnCompositor = property.mIsRunningOnCompositor;
 
-    nsXPIDLString localizedString;
+    nsAutoString localizedString;
     if (property.mPerformanceWarning &&
         property.mPerformanceWarning->ToLocalizedString(localizedString)) {
       propertyDetails.mWarning.Construct(localizedString);
@@ -1621,7 +1621,7 @@ KeyframeEffectReadOnly::SetPerformanceWarning(
          *property.mPerformanceWarning != aWarning)) {
       property.mPerformanceWarning = Some(aWarning);
 
-      nsXPIDLString localizedString;
+      nsAutoString localizedString;
       if (nsLayoutUtils::IsAnimationLoggingEnabled() &&
           property.mPerformanceWarning->ToLocalizedString(localizedString)) {
         nsAutoCString logMessage = NS_ConvertUTF16toUTF8(localizedString);
diff --git a/dom/base/EventSource.cpp b/dom/base/EventSource.cpp
index 2c23da6ab414..c8b265f788c9 100644
--- a/dom/base/EventSource.cpp
+++ b/dom/base/EventSource.cpp
@@ -1243,13 +1243,12 @@ EventSourceImpl::PrintErrorOnConsole(const char* aBundleURI,
   NS_ENSURE_SUCCESS(rv, rv);
 
   // Localize the error message
-  nsXPIDLString message;
+  nsAutoString message;
   if (aFormatStrings) {
     rv = strBundle->FormatStringFromName(aError, aFormatStrings,
-                                         aFormatStringsLen,
-                                         getter_Copies(message));
+                                         aFormatStringsLen, message);
   } else {
-    rv = strBundle->GetStringFromName(aError, getter_Copies(message));
+    rv = strBundle->GetStringFromName(aError, message);
   }
   NS_ENSURE_SUCCESS(rv, rv);
 
diff --git a/dom/base/WebSocket.cpp b/dom/base/WebSocket.cpp
index 143702c68ce5..c579d0149de2 100644
--- a/dom/base/WebSocket.cpp
+++ b/dom/base/WebSocket.cpp
@@ -371,13 +371,12 @@ WebSocketImpl::PrintErrorOnConsole(const char *aBundleURI,
   NS_ENSURE_SUCCESS_VOID(rv);
 
   // Localize the error message
-  nsXPIDLString message;
+  nsAutoString message;
   if (aFormatStrings) {
     rv = strBundle->FormatStringFromName(aError, aFormatStrings,
-                                         aFormatStringsLen,
-                                         getter_Copies(message));
+                                         aFormatStringsLen, message);
   } else {
-    rv = strBundle->GetStringFromName(aError, getter_Copies(message));
+    rv = strBundle->GetStringFromName(aError, message);
   }
   NS_ENSURE_SUCCESS_VOID(rv);
 
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index acdcc27371d0..dc77a50364ce 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -864,20 +864,20 @@ nsContentUtils::InitializeModifierStrings()
   }
 
   NS_ASSERTION(NS_SUCCEEDED(rv) && bundle, "chrome://global/locale/platformKeys.properties could not be loaded");
-  nsXPIDLString shiftModifier;
-  nsXPIDLString metaModifier;
-  nsXPIDLString osModifier;
-  nsXPIDLString altModifier;
-  nsXPIDLString controlModifier;
-  nsXPIDLString modifierSeparator;
+  nsAutoString shiftModifier;
+  nsAutoString metaModifier;
+  nsAutoString osModifier;
+  nsAutoString altModifier;
+  nsAutoString controlModifier;
+  nsAutoString modifierSeparator;
   if (bundle) {
     //macs use symbols for each modifier key, so fetch each from the bundle, which also covers i18n
-    bundle->GetStringFromName("VK_SHIFT", getter_Copies(shiftModifier));
-    bundle->GetStringFromName("VK_META", getter_Copies(metaModifier));
-    bundle->GetStringFromName("VK_WIN", getter_Copies(osModifier));
-    bundle->GetStringFromName("VK_ALT", getter_Copies(altModifier));
-    bundle->GetStringFromName("VK_CONTROL", getter_Copies(controlModifier));
-    bundle->GetStringFromName("MODIFIER_SEPARATOR", getter_Copies(modifierSeparator));
+    bundle->GetStringFromName("VK_SHIFT", shiftModifier);
+    bundle->GetStringFromName("VK_META", metaModifier);
+    bundle->GetStringFromName("VK_WIN", osModifier);
+    bundle->GetStringFromName("VK_ALT", altModifier);
+    bundle->GetStringFromName("VK_CONTROL", controlModifier);
+    bundle->GetStringFromName("MODIFIER_SEPARATOR", modifierSeparator);
   }
   //if any of these don't exist, we get  an empty string
   sShiftText = new nsString(shiftModifier);
@@ -3957,13 +3957,12 @@ nsContentUtils::EnsureStringBundle(PropertiesFile aFile)
 /* static */
 nsresult nsContentUtils::GetLocalizedString(PropertiesFile aFile,
                                             const char* aKey,
-                                            nsXPIDLString& aResult)
+                                            nsAString& aResult)
 {
   nsresult rv = EnsureStringBundle(aFile);
   NS_ENSURE_SUCCESS(rv, rv);
   nsIStringBundle *bundle = sStringBundles[aFile];
-
-  return bundle->GetStringFromName(aKey, getter_Copies(aResult));
+  return bundle->GetStringFromName(aKey, aResult);
 }
 
 /* static */
@@ -3971,19 +3970,17 @@ nsresult nsContentUtils::FormatLocalizedString(PropertiesFile aFile,
                                                const char* aKey,
                                                const char16_t **aParams,
                                                uint32_t aParamsLength,
-                                               nsXPIDLString& aResult)
+                                               nsAString& aResult)
 {
   nsresult rv = EnsureStringBundle(aFile);
   NS_ENSURE_SUCCESS(rv, rv);
   nsIStringBundle *bundle = sStringBundles[aFile];
 
   if (!aParams || !aParamsLength) {
-    return bundle->GetStringFromName(aKey, getter_Copies(aResult));
+    return bundle->GetStringFromName(aKey, aResult);
   }
 
-  return bundle->FormatStringFromName(aKey,
-                                      aParams, aParamsLength,
-                                      getter_Copies(aResult));
+  return bundle->FormatStringFromName(aKey, aParams, aParamsLength, aResult);
 }
 
 /* static */
@@ -3991,7 +3988,7 @@ nsresult nsContentUtils::FormatLocalizedString(
                                           PropertiesFile aFile,
                                           const char* aKey,
                                           const nsTArray<nsString>& aParamArray,
-                                          nsXPIDLString& aResult)
+                                          nsAString& aResult)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
@@ -4044,7 +4041,7 @@ nsContentUtils::ReportToConsole(uint32_t aErrorFlags,
                "parameters and 0.");
 
   nsresult rv;
-  nsXPIDLString errorText;
+  nsAutoString errorText;
   if (aParams) {
     rv = FormatLocalizedString(aFile, aMessageName, aParams, aParamsLength,
                                errorText);
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index fe7b5ab0ef08..47260e7e4d3c 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -1040,7 +1040,7 @@ public:
    */
   static nsresult GetLocalizedString(PropertiesFile aFile,
                                      const char* aKey,
-                                     nsXPIDLString& aResult);
+                                     nsAString& aResult);
 
   /**
    * A helper function that parses a sandbox attribute (of an <iframe> or a CSP
@@ -1086,14 +1086,14 @@ private:
                                         const char* aKey,
                                         const char16_t** aParams,
                                         uint32_t aParamsLength,
-                                        nsXPIDLString& aResult);
+                                        nsAString& aResult);
 
 public:
   template<uint32_t N>
   static nsresult FormatLocalizedString(PropertiesFile aFile,
                                         const char* aKey,
                                         const char16_t* (&aParams)[N],
-                                        nsXPIDLString& aResult)
+                                        nsAString& aResult)
   {
     return FormatLocalizedString(aFile, aKey, aParams, N, aResult);
   }
@@ -1107,7 +1107,7 @@ public:
   static nsresult FormatLocalizedString(PropertiesFile aFile,
                                         const char* aKey,
                                         const nsTArray<nsString>& aParamArray,
-                                        nsXPIDLString& aResult);
+                                        nsAString& aResult);
 
   /**
    * Returns true if aDocument is a chrome document
diff --git a/dom/base/nsGlobalWindow.cpp b/dom/base/nsGlobalWindow.cpp
index a6fb60d13965..0bead866f631 100644
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@@ -3894,7 +3894,7 @@ nsGlobalWindow::ConfirmDialogIfNeeded()
   nsAutoPopupStatePusher popupStatePusher(openAbused, true);
 
   bool disableDialog = false;
-  nsXPIDLString label, title;
+  nsAutoString label, title;
   nsContentUtils::GetLocalizedString(nsContentUtils::eCOMMON_DIALOG_PROPERTIES,
                                      "ScriptDialogLabel", label);
   nsContentUtils::GetLocalizedString(nsContentUtils::eCOMMON_DIALOG_PROPERTIES,
@@ -7508,12 +7508,10 @@ nsGlobalWindow::MakeScriptDialogTitle(nsAString& aOutTitle,
 
           NS_ConvertUTF8toUTF16 ucsPrePath(prepath);
           const char16_t *formatStrings[] = { ucsPrePath.get() };
-          nsXPIDLString tempString;
           nsContentUtils::FormatLocalizedString(nsContentUtils::eCOMMON_DIALOG_PROPERTIES,
                                                 "ScriptDlgHeading",
                                                 formatStrings,
-                                                tempString);
-          aOutTitle = tempString;
+                                                aOutTitle);
         }
       }
     }
@@ -7521,11 +7519,9 @@ nsGlobalWindow::MakeScriptDialogTitle(nsAString& aOutTitle,
 
   if (aOutTitle.IsEmpty()) {
     // We didn't find a host so use the generic heading
-    nsXPIDLString tempString;
     nsContentUtils::GetLocalizedString(nsContentUtils::eCOMMON_DIALOG_PROPERTIES,
                                        "ScriptDlgGenericHeading",
-                                       tempString);
-    aOutTitle = tempString;
+                                       aOutTitle);
   }
 
   // Just in case
@@ -7649,7 +7645,7 @@ nsGlobalWindow::AlertOrConfirm(bool aAlert,
   nsAutoSyncOperation sync(mDoc);
   if (ShouldPromptToBlockDialogs()) {
     bool disallowDialog = false;
-    nsXPIDLString label;
+    nsAutoString label;
     nsContentUtils::GetLocalizedString(nsContentUtils::eCOMMON_DIALOG_PROPERTIES,
                                        "ScriptDialogLabel", label);
 
@@ -7784,7 +7780,8 @@ nsGlobalWindow::PromptOuter(const nsAString& aMessage,
   char16_t *inoutValue = ToNewUnicode(fixedInitial);
   bool disallowDialog = false;
 
-  nsXPIDLString label;
+  nsAutoString label;
+  label.SetIsVoid(true);
   if (ShouldPromptToBlockDialogs()) {
     nsContentUtils::GetLocalizedString(nsContentUtils::eCOMMON_DIALOG_PROPERTIES,
                                        "ScriptDialogLabel", label);
@@ -7792,8 +7789,9 @@ nsGlobalWindow::PromptOuter(const nsAString& aMessage,
 
   nsAutoSyncOperation sync(mDoc);
   bool ok;
-  aError = prompt->Prompt(title.get(), fixedMessage.get(),
-                          &inoutValue, label.get(), &disallowDialog, &ok);
+  aError = prompt->Prompt(title.get(), fixedMessage.get(), &inoutValue,
+                          label.IsVoid() ? nullptr : label.get(),
+                          &disallowDialog, &ok);
 
   if (disallowDialog) {
     DisableDialogs();
@@ -8144,7 +8142,7 @@ nsGlobalWindow::PrintOuter(ErrorResult& aError)
       if (printSettingsAreGlobal) {
         printSettingsService->GetGlobalPrintSettings(getter_AddRefs(printSettings));
 
-        nsXPIDLString printerName;
+        nsAutoString printerName;
         printSettings->GetPrinterName(getter_Copies(printerName));
 
         bool shouldGetDefaultPrinterName = printerName.IsEmpty();
@@ -8160,9 +8158,10 @@ nsGlobalWindow::PrintOuter(ErrorResult& aError)
 #endif
         if (shouldGetDefaultPrinterName) {
           printSettingsService->GetDefaultPrinterName(getter_Copies(printerName));
-          printSettings->SetPrinterName(printerName);
+          printSettings->SetPrinterName(printerName.get());
         }
-        printSettingsService->InitPrintSettingsFromPrinter(printerName, printSettings);
+        printSettingsService->InitPrintSettingsFromPrinter(printerName.get(),
+                                                           printSettings);
         printSettingsService->InitPrintSettingsFromPrefs(printSettings,
                                                          true,
                                                          nsIPrintSettings::kInitSaveAll);
@@ -11956,7 +11955,7 @@ nsGlobalWindow::ShowSlowScriptDialog()
   bool showDebugButton = !!debugCallback;
 
   // Get localizable strings
-  nsXPIDLString title, msg, stopButton, waitButton, debugButton, neverShowDlg;
+  nsAutoString title, msg, stopButton, waitButton, debugButton, neverShowDlg;
 
   rv = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                           "KillScriptTitle",
@@ -11983,7 +11982,6 @@ nsGlobalWindow::ShowSlowScriptDialog()
     rv = tmp;
   }
 
-
   if (showDebugButton) {
     tmp = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                              "DebugScriptButton",
@@ -12008,16 +12006,14 @@ nsGlobalWindow::ShowSlowScriptDialog()
     }
   }
 
-  // GetStringFromName can return NS_OK and still give nullptr string
-  if (NS_FAILED(rv) || !title || !msg || !stopButton || !waitButton ||
-      (!debugButton && showDebugButton) || !neverShowDlg) {
+  if (NS_FAILED(rv)) {
     NS_ERROR("Failed to get localized strings.");
     return ContinueSlowScript;
   }
 
   // Append file and line number information, if available
   if (filename.get()) {
-    nsXPIDLString scriptLocation;
+    nsAutoString scriptLocation;
     // We want to drop the middle part of too-long locations.  We'll
     // define "too-long" as longer than 60 UTF-16 code units.  Just
     // have to be a bit careful about unpaired surrogates.
@@ -12050,7 +12046,7 @@ nsGlobalWindow::ShowSlowScriptDialog()
                                                formatParams,
                                                scriptLocation);
 
-    if (NS_SUCCEEDED(rv) && scriptLocation) {
+    if (NS_SUCCEEDED(rv)) {
       msg.AppendLiteral("\n\n");
       msg.Append(scriptLocation);
       msg.Append(':');
@@ -12072,9 +12068,10 @@ nsGlobalWindow::ShowSlowScriptDialog()
     // Null out the operation callback while we're re-entering JS here.
     AutoDisableJSInterruptCallback disabler(cx);
     // Open the dialog.
-    rv = prompt->ConfirmEx(title, msg, buttonFlags, waitButton, stopButton,
-                          debugButton, neverShowDlg, &neverShowDlgChk,
-                          &buttonPressed);
+    rv = prompt->ConfirmEx(title.get(), msg.get(), buttonFlags,
+                           waitButton.get(), stopButton.get(),
+                           debugButton.get(), neverShowDlg.get(),
+                           &neverShowDlgChk, &buttonPressed);
   }
 
   if (NS_SUCCEEDED(rv) && (buttonPressed == 0)) {
diff --git a/dom/base/test/FAIL.html b/dom/base/test/FAIL.html
new file mode 100644
index 000000000000..94e1707e853c
--- /dev/null
+++ b/dom/base/test/FAIL.html
@@ -0,0 +1 @@
+FAIL
diff --git a/dom/base/test/mochitest.ini b/dom/base/test/mochitest.ini
index 2e7d51ce4c91..2c2764619b44 100644
--- a/dom/base/test/mochitest.ini
+++ b/dom/base/test/mochitest.ini
@@ -248,6 +248,7 @@ support-files =
   file3_setting_opener.html
   file4_setting_opener.html
   PASS.html
+  FAIL.html
   window_bug1384658.html
 
 [test_anchor_area_referrer.html]
diff --git a/dom/base/test/test_bug331959.html b/dom/base/test/test_bug331959.html
index 20c447f51177..4d417cefb7bf 100644
--- a/dom/base/test/test_bug331959.html
+++ b/dom/base/test/test_bug331959.html
@@ -28,8 +28,8 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=331959
 /** Test for Bug 331959 **/
 SimpleTest.waitForExplicitFinish();
 
-const FAILURL = "data:text/plain,FAIL";
-const PASSURL = "data:text/plain,PASS";
+const FAILURL = "FAIL.html";
+const PASSURL = "PASS.html";
 
 var currentTest = 0;
 var tests = [ testLinkInLinkMouse, testLinkInLinkKeyboard,
@@ -55,7 +55,7 @@ function generateLinkInLink(id, desc) {
   outerA.appendChild(innerA);
   doc.body.appendChild(outerA);
   $(id).onload = function() {
-    is(this.contentDocument.documentElement.textContent, "PASS", desc);
+    is(this.contentDocument.documentElement.innerText, "PASS", desc);
     // Have to remove the iframe we used from the DOM, because the harness is
     // stupid and doesn't have enough space for more than one iframe.
     $(id).remove();
@@ -85,7 +85,7 @@ function generateInputInLink(id, desc) {
     "<form action='" + PASSURL + "'><a href='" + FAILURL +
     "'><input type='submit' id='submit'>";
   $(id).onload = function() {
-    is(this.contentDocument.documentElement.textContent, "PASS?", desc);
+    is(this.contentDocument.documentElement.innerText, "PASS", desc);
     // Have to remove the iframe we used from the DOM, because the harness is
     // stupid and doesn't have enough space for more than one iframe.
     $(id).remove();
@@ -117,7 +117,7 @@ function generateButtonInLink(id, desc) {
     "<form action='" + PASSURL + "'><a href='" + FAILURL +
     "'><button type='submit' id='submit'>Submit</button>";
   $(id).onload = function() {
-    is(this.contentDocument.documentElement.textContent, "PASS?", desc);
+    is(this.contentDocument.documentElement.innerText, "PASS", desc);
     // Have to remove the iframe we used from the DOM, because the harness is
     // stupid and doesn't have enough space for more than one iframe.
     $(id).remove();
diff --git a/dom/console/ConsoleReportCollector.cpp b/dom/console/ConsoleReportCollector.cpp
index 10cee116434c..dfa99f5876ac 100644
--- a/dom/console/ConsoleReportCollector.cpp
+++ b/dom/console/ConsoleReportCollector.cpp
@@ -56,7 +56,7 @@ ConsoleReportCollector::FlushReportsToConsole(uint64_t aInnerWindowID,
   for (uint32_t i = 0; i < reports.Length(); ++i) {
     PendingReport& report = reports[i];
 
-    nsXPIDLString errorText;
+    nsAutoString errorText;
     nsresult rv;
     if (!report.mStringParams.IsEmpty()) {
       rv = nsContentUtils::FormatLocalizedString(report.mPropertiesFile,
diff --git a/dom/events/DataTransferItem.cpp b/dom/events/DataTransferItem.cpp
index 3b2f4509c348..80f4a5b3095a 100644
--- a/dom/events/DataTransferItem.cpp
+++ b/dom/events/DataTransferItem.cpp
@@ -388,7 +388,7 @@ DataTransferItem::CreateFileFromInputStream(nsIInputStream* aStream)
     key = "GenericFileName";
   }
 
-  nsXPIDLString fileName;
+  nsAutoString fileName;
   nsresult rv = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                                    key, fileName);
   if (NS_WARN_IF(NS_FAILED(rv))) {
diff --git a/dom/html/HTMLFormElement.cpp b/dom/html/HTMLFormElement.cpp
index 4687415f84e5..58405b6ae050 100644
--- a/dom/html/HTMLFormElement.cpp
+++ b/dom/html/HTMLFormElement.cpp
@@ -919,11 +919,11 @@ HTMLFormElement::DoSecureToInsecureSubmitCheck(nsIURI* aActionURL,
   nsAutoString message;
   nsAutoString cont;
   stringBundle->GetStringFromName(
-    "formPostSecureToInsecureWarning.title", getter_Copies(title));
+    "formPostSecureToInsecureWarning.title", title);
   stringBundle->GetStringFromName(
-    "formPostSecureToInsecureWarning.message", getter_Copies(message));
+    "formPostSecureToInsecureWarning.message", message);
   stringBundle->GetStringFromName(
-    "formPostSecureToInsecureWarning.continue", getter_Copies(cont));
+    "formPostSecureToInsecureWarning.continue", cont);
   int32_t buttonPressed;
   bool checkState = false; // this is unused (ConfirmEx requires this parameter)
   rv = prompt->ConfirmEx(title.get(), message.get(),
diff --git a/dom/html/HTMLFormSubmission.cpp b/dom/html/HTMLFormSubmission.cpp
index 01caccaeaaf5..a989daab8974 100644
--- a/dom/html/HTMLFormSubmission.cpp
+++ b/dom/html/HTMLFormSubmission.cpp
@@ -238,14 +238,14 @@ HandleMailtoSubject(nsCString& aPath)
     }
 
     // Get the default subject
-    nsXPIDLString brandName;
+    nsAutoString brandName;
     nsresult rv =
       nsContentUtils::GetLocalizedString(nsContentUtils::eBRAND_PROPERTIES,
                                          "brandShortName", brandName);
     if (NS_FAILED(rv))
       return;
     const char16_t *formatStrings[] = { brandName.get() };
-    nsXPIDLString subjectStr;
+    nsAutoString subjectStr;
     rv = nsContentUtils::FormatLocalizedString(
                                            nsContentUtils::eFORMS_PROPERTIES,
                                            "DefaultFormSubject",
diff --git a/dom/html/HTMLInputElement.cpp b/dom/html/HTMLInputElement.cpp
index 29eebfe61876..1f4bb9d0277d 100644
--- a/dom/html/HTMLInputElement.cpp
+++ b/dom/html/HTMLInputElement.cpp
@@ -854,7 +854,7 @@ HTMLInputElement::InitColorPicker()
   }
 
   // Get Loc title
-  nsXPIDLString title;
+  nsAutoString title;
   nsContentUtils::GetLocalizedString(nsContentUtils::eFORMS_PROPERTIES,
                                      "ColorPicker", title);
 
@@ -901,8 +901,8 @@ HTMLInputElement::InitFilePicker(FilePickerType aType)
   }
 
   // Get Loc title
-  nsXPIDLString title;
-  nsXPIDLString okButtonLabel;
+  nsAutoString title;
+  nsAutoString okButtonLabel;
   if (aType == FILE_PICKER_DIRECTORY) {
     nsContentUtils::GetLocalizedString(nsContentUtils::eFORMS_PROPERTIES,
                                        "DirectoryUpload", title);
@@ -2769,7 +2769,7 @@ HTMLInputElement::GetDisplayFileName(nsAString& aValue) const
     return;
   }
 
-  nsXPIDLString value;
+  nsAutoString value;
 
   if (mFileData->mFilesOrDirectories.IsEmpty()) {
     if ((IsDirPickerEnabled() && Allowdirs()) ||
@@ -6415,7 +6415,7 @@ HTMLInputElement::SubmitNamesValues(HTMLFormSubmission* aFormSubmission)
   if (mType == NS_FORM_INPUT_SUBMIT && value.IsEmpty() &&
       !HasAttr(kNameSpaceID_None, nsGkAtoms::value)) {
     // Get our default value, which is the same as our default label
-    nsXPIDLString defaultValue;
+    nsAutoString defaultValue;
     nsContentUtils::GetLocalizedString(nsContentUtils::eFORMS_PROPERTIES,
                                        "Submit", defaultValue);
     value = defaultValue;
@@ -7570,15 +7570,15 @@ HTMLInputElement::SetFilePickerFiltersFromAccept(nsIFilePicker* filePicker)
     if (token.EqualsLiteral("image/*")) {
       filterMask = nsIFilePicker::filterImages;
       filterBundle->GetStringFromName("imageFilter",
-                                      getter_Copies(extensionListStr));
+                                      extensionListStr);
     } else if (token.EqualsLiteral("audio/*")) {
       filterMask = nsIFilePicker::filterAudio;
       filterBundle->GetStringFromName("audioFilter",
-                                      getter_Copies(extensionListStr));
+                                      extensionListStr);
     } else if (token.EqualsLiteral("video/*")) {
       filterMask = nsIFilePicker::filterVideo;
       filterBundle->GetStringFromName("videoFilter",
-                                      getter_Copies(extensionListStr));
+                                      extensionListStr);
     } else if (token.First() == '.') {
       if (token.Contains(';') || token.Contains('*')) {
         // Ignore this filter as it contains reserved characters
@@ -7681,7 +7681,7 @@ HTMLInputElement::SetFilePickerFiltersFromAccept(nsIFilePicker* filePicker)
 
   // Add "All Supported Types" filter
   if (filters.Length() > 1) {
-    nsXPIDLString title;
+    nsAutoString title;
     nsContentUtils::GetLocalizedString(nsContentUtils::eFORMS_PROPERTIES,
                                        "AllSupportedTypes", title);
     filePicker->AppendFilter(title, allExtensionsList);
diff --git a/dom/html/HTMLSelectElement.cpp b/dom/html/HTMLSelectElement.cpp
index 1076d3afc3ef..a025232dd149 100644
--- a/dom/html/HTMLSelectElement.cpp
+++ b/dom/html/HTMLSelectElement.cpp
@@ -1825,7 +1825,7 @@ HTMLSelectElement::GetValidationMessage(nsAString& aValidationMessage,
 {
   switch (aType) {
     case VALIDITY_STATE_VALUE_MISSING: {
-      nsXPIDLString message;
+      nsAutoString message;
       nsresult rv = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                                        "FormValidationSelectMissing",
                                                        message);
diff --git a/dom/html/HTMLTextAreaElement.cpp b/dom/html/HTMLTextAreaElement.cpp
index 2ccb1567c18b..f42a0ecb66e3 100644
--- a/dom/html/HTMLTextAreaElement.cpp
+++ b/dom/html/HTMLTextAreaElement.cpp
@@ -1262,7 +1262,7 @@ HTMLTextAreaElement::GetValidationMessage(nsAString& aValidationMessage,
   {
     case VALIDITY_STATE_TOO_LONG:
       {
-        nsXPIDLString message;
+        nsAutoString message;
         int32_t maxLength = -1;
         int32_t textLength = -1;
         nsAutoString strMaxLength;
@@ -1283,7 +1283,7 @@ HTMLTextAreaElement::GetValidationMessage(nsAString& aValidationMessage,
       break;
     case VALIDITY_STATE_TOO_SHORT:
       {
-        nsXPIDLString message;
+        nsAutoString message;
         int32_t minLength = -1;
         int32_t textLength = -1;
         nsAutoString strMinLength;
@@ -1304,7 +1304,7 @@ HTMLTextAreaElement::GetValidationMessage(nsAString& aValidationMessage,
       break;
     case VALIDITY_STATE_VALUE_MISSING:
       {
-        nsXPIDLString message;
+        nsAutoString message;
         rv = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                                 "FormValidationValueMissing",
                                                 message);
diff --git a/dom/html/ImageDocument.cpp b/dom/html/ImageDocument.cpp
index b9f8b2d98abf..7d3f5267290f 100644
--- a/dom/html/ImageDocument.cpp
+++ b/dom/html/ImageDocument.cpp
@@ -599,9 +599,9 @@ ImageDocument::OnLoadComplete(imgIRequest* aRequest, nsresult aStatus)
     mDocumentURI->GetSpec(src);
     NS_ConvertUTF8toUTF16 srcString(src);
     const char16_t* formatString[] = { srcString.get() };
-    nsXPIDLString errorMsg;
+    nsAutoString errorMsg;
     mStringBundle->FormatStringFromName("InvalidImage", formatString, 1,
-                                        getter_Copies(errorMsg));
+                                        errorMsg);
 
     mImageContent->SetAttr(kNameSpaceID_None, nsGkAtoms::alt, errorMsg, false);
   }
@@ -805,15 +805,13 @@ ImageDocument::UpdateTitleAndCharset()
     }
   }
 
-  nsXPIDLString status;
+  nsAutoString status;
   if (mImageIsResized) {
     nsAutoString ratioStr;
     ratioStr.AppendInt(NSToCoordFloor(GetRatio() * 100));
 
     const char16_t* formatString[1] = { ratioStr.get() };
-    mStringBundle->FormatStringFromName("ScaledImage",
-                                        formatString, 1,
-                                        getter_Copies(status));
+    mStringBundle->FormatStringFromName("ScaledImage", formatString, 1, status);
   }
 
   static const char* const formatNames[4] =
diff --git a/dom/html/MediaDocument.cpp b/dom/html/MediaDocument.cpp
index 60fa5694c4da..716111f4bac0 100644
--- a/dom/html/MediaDocument.cpp
+++ b/dom/html/MediaDocument.cpp
@@ -365,7 +365,7 @@ MediaDocument::UpdateTitleAndCharset(const nsACString& aTypeStr,
   GetFileName(fileStr, aChannel);
 
   NS_ConvertASCIItoUTF16 typeStr(aTypeStr);
-  nsXPIDLString title;
+  nsAutoString title;
 
   if (mStringBundle) {
     // if we got a valid size (not all media have a size)
@@ -379,15 +379,13 @@ MediaDocument::UpdateTitleAndCharset(const nsACString& aTypeStr,
         const char16_t *formatStrings[4]  = {fileStr.get(), typeStr.get(),
           widthStr.get(), heightStr.get()};
         mStringBundle->FormatStringFromName(aFormatNames[eWithDimAndFile],
-                                            formatStrings, 4,
-                                            getter_Copies(title));
+                                            formatStrings, 4, title);
       }
       else {
         const char16_t *formatStrings[3]  = {typeStr.get(), widthStr.get(),
           heightStr.get()};
         mStringBundle->FormatStringFromName(aFormatNames[eWithDim],
-                                            formatStrings, 3,
-                                            getter_Copies(title));
+                                            formatStrings, 3, title);
       }
     }
     else {
@@ -395,14 +393,12 @@ MediaDocument::UpdateTitleAndCharset(const nsACString& aTypeStr,
       if (!fileStr.IsEmpty()) {
         const char16_t *formatStrings[2] = {fileStr.get(), typeStr.get()};
         mStringBundle->FormatStringFromName(aFormatNames[eWithFile],
-                                            formatStrings, 2,
-                                            getter_Copies(title));
+                                            formatStrings, 2, title);
       }
       else {
         const char16_t *formatStrings[1] = {typeStr.get()};
         mStringBundle->FormatStringFromName(aFormatNames[eWithNoInfo],
-                                            formatStrings, 1,
-                                            getter_Copies(title));
+                                            formatStrings, 1, title);
       }
     }
   }
@@ -412,11 +408,11 @@ MediaDocument::UpdateTitleAndCharset(const nsACString& aTypeStr,
     SetTitle(title);
   }
   else {
-    nsXPIDLString titleWithStatus;
+    nsAutoString titleWithStatus;
     const nsPromiseFlatString& status = PromiseFlatString(aStatus);
     const char16_t *formatStrings[2] = {title.get(), status.get()};
     mStringBundle->FormatStringFromName("TitleWithStatus", formatStrings,
-                                        2, getter_Copies(titleWithStatus));
+                                        2, titleWithStatus);
     SetTitle(titleWithStatus);
   }
 }
diff --git a/dom/html/input/CheckableInputTypes.cpp b/dom/html/input/CheckableInputTypes.cpp
index e261b8faac5a..8699e0744816 100644
--- a/dom/html/input/CheckableInputTypes.cpp
+++ b/dom/html/input/CheckableInputTypes.cpp
@@ -25,7 +25,7 @@ CheckboxInputType::IsValueMissing() const
 }
 
 nsresult
-CheckboxInputType::GetValueMissingMessage(nsXPIDLString& aMessage)
+CheckboxInputType::GetValueMissingMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                             "FormValidationCheckboxMissing",
@@ -35,7 +35,7 @@ CheckboxInputType::GetValueMissingMessage(nsXPIDLString& aMessage)
 /* input type=radio */
 
 nsresult
-RadioInputType::GetValueMissingMessage(nsXPIDLString& aMessage)
+RadioInputType::GetValueMissingMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                             "FormValidationRadioMissing",
diff --git a/dom/html/input/CheckableInputTypes.h b/dom/html/input/CheckableInputTypes.h
index 8cd6e396d3e1..e004ea8e1851 100644
--- a/dom/html/input/CheckableInputTypes.h
+++ b/dom/html/input/CheckableInputTypes.h
@@ -32,7 +32,7 @@ public:
 
   bool IsValueMissing() const override;
 
-  nsresult GetValueMissingMessage(nsXPIDLString& aMessage) override;
+  nsresult GetValueMissingMessage(nsAString& aMessage) override;
 
 private:
   explicit CheckboxInputType(mozilla::dom::HTMLInputElement* aInputElement)
@@ -50,7 +50,7 @@ public:
     return new (aMemory) RadioInputType(aInputElement);
   }
 
-  nsresult GetValueMissingMessage(nsXPIDLString& aMessage) override;
+  nsresult GetValueMissingMessage(nsAString& aMessage) override;
 
 private:
   explicit RadioInputType(mozilla::dom::HTMLInputElement* aInputElement)
diff --git a/dom/html/input/DateTimeInputTypes.cpp b/dom/html/input/DateTimeInputTypes.cpp
index 85cf3ef0a294..c136fd99be37 100644
--- a/dom/html/input/DateTimeInputTypes.cpp
+++ b/dom/html/input/DateTimeInputTypes.cpp
@@ -118,7 +118,7 @@ DateTimeInputTypeBase::HasBadInput() const
 }
 
 nsresult
-DateTimeInputTypeBase::GetRangeOverflowMessage(nsXPIDLString& aMessage)
+DateTimeInputTypeBase::GetRangeOverflowMessage(nsAString& aMessage)
 {
   nsAutoString maxStr;
   mInputElement->GetAttr(kNameSpaceID_None, nsGkAtoms::max, maxStr);
@@ -129,7 +129,7 @@ DateTimeInputTypeBase::GetRangeOverflowMessage(nsXPIDLString& aMessage)
 }
 
 nsresult
-DateTimeInputTypeBase::GetRangeUnderflowMessage(nsXPIDLString& aMessage)
+DateTimeInputTypeBase::GetRangeUnderflowMessage(nsAString& aMessage)
 {
   nsAutoString minStr;
   mInputElement->GetAttr(kNameSpaceID_None, nsGkAtoms::min, minStr);
@@ -176,7 +176,7 @@ DateTimeInputTypeBase::GetTimeFromMs(double aValue, uint16_t* aHours,
 // input type=date
 
 nsresult
-DateInputType::GetBadInputMessage(nsXPIDLString& aMessage)
+DateInputType::GetBadInputMessage(nsAString& aMessage)
 {
   if (!IsInputDateTimeEnabled()) {
     return NS_ERROR_UNEXPECTED;
diff --git a/dom/html/input/DateTimeInputTypes.h b/dom/html/input/DateTimeInputTypes.h
index b53cb3485efc..a399f22aa4e6 100644
--- a/dom/html/input/DateTimeInputTypes.h
+++ b/dom/html/input/DateTimeInputTypes.h
@@ -20,8 +20,8 @@ public:
   bool HasStepMismatch(bool aUseZeroIfValueNaN) const override;
   bool HasBadInput() const override;
 
-  nsresult GetRangeOverflowMessage(nsXPIDLString& aMessage) override;
-  nsresult GetRangeUnderflowMessage(nsXPIDLString& aMessage) override;
+  nsresult GetRangeOverflowMessage(nsAString& aMessage) override;
+  nsresult GetRangeUnderflowMessage(nsAString& aMessage) override;
 
   nsresult MinMaxStepAttrChanged() override;
 
@@ -71,7 +71,7 @@ public:
   // we forbid or autocorrect values that are not in the valid range for time.
   // For example, in 12hr format, if user enters '2' in the hour field, it will
   // be treated as '02' and automatically advance to the next field.
-  nsresult GetBadInputMessage(nsXPIDLString& aMessage) override;
+  nsresult GetBadInputMessage(nsAString& aMessage) override;
 
   bool ConvertStringToNumber(nsAString& aValue,
                              mozilla::Decimal& aResultValue) const override;
diff --git a/dom/html/input/FileInputType.cpp b/dom/html/input/FileInputType.cpp
index 0a9ee5ce5d5b..51365156bc27 100644
--- a/dom/html/input/FileInputType.cpp
+++ b/dom/html/input/FileInputType.cpp
@@ -23,7 +23,7 @@ FileInputType::IsValueMissing() const
 }
 
 nsresult
-FileInputType::GetValueMissingMessage(nsXPIDLString& aMessage)
+FileInputType::GetValueMissingMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                             "FormValidationFileMissing",
diff --git a/dom/html/input/FileInputType.h b/dom/html/input/FileInputType.h
index 892c5296f637..7398362fe7f9 100644
--- a/dom/html/input/FileInputType.h
+++ b/dom/html/input/FileInputType.h
@@ -21,7 +21,7 @@ public:
 
   bool IsValueMissing() const override;
 
-  nsresult GetValueMissingMessage(nsXPIDLString& aMessage) override;
+  nsresult GetValueMissingMessage(nsAString& aMessage) override;
 
 private:
   explicit FileInputType(mozilla::dom::HTMLInputElement* aInputElement)
diff --git a/dom/html/input/InputType.cpp b/dom/html/input/InputType.cpp
index 4f2d917ef9bc..1ffeca40e0f5 100644
--- a/dom/html/input/InputType.cpp
+++ b/dom/html/input/InputType.cpp
@@ -212,7 +212,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
   {
     case nsIConstraintValidation::VALIDITY_STATE_TOO_LONG:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       int32_t maxLength = mInputElement->MaxLength();
       int32_t textLength =
         mInputElement->InputTextLength(mozilla::dom::CallerType::System);
@@ -231,7 +231,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_TOO_SHORT:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       int32_t minLength = mInputElement->MinLength();
       int32_t textLength =
         mInputElement->InputTextLength(mozilla::dom::CallerType::System);
@@ -251,7 +251,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_VALUE_MISSING:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       rv = GetValueMissingMessage(message);
       if (NS_FAILED(rv)) {
         return rv;
@@ -262,7 +262,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_TYPE_MISMATCH:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       rv = GetTypeMismatchMessage(message);
       if (NS_FAILED(rv)) {
         return rv;
@@ -273,7 +273,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_PATTERN_MISMATCH:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       nsAutoString title;
       mInputElement->GetAttr(kNameSpaceID_None, nsGkAtoms::title, title);
       if (title.IsEmpty()) {
@@ -295,7 +295,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_RANGE_OVERFLOW:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       rv = GetRangeOverflowMessage(message);
       if (NS_FAILED(rv)) {
         return rv;
@@ -306,7 +306,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_RANGE_UNDERFLOW:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       rv = GetRangeUnderflowMessage(message);
       if (NS_FAILED(rv)) {
         return rv;
@@ -317,7 +317,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_STEP_MISMATCH:
     {
-      nsXPIDLString message;
+      nsAutoString message;
 
       mozilla::Decimal value = mInputElement->GetValueAsDecimal();
       MOZ_ASSERT(!value.isNaN());
@@ -365,7 +365,7 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
     }
     case nsIConstraintValidation::VALIDITY_STATE_BAD_INPUT:
     {
-      nsXPIDLString message;
+      nsAutoString message;
       rv = GetBadInputMessage(message);
       if (NS_FAILED(rv)) {
         return rv;
@@ -382,32 +382,32 @@ InputType::GetValidationMessage(nsAString& aValidationMessage,
 }
 
 nsresult
-InputType::GetValueMissingMessage(nsXPIDLString& aMessage)
+InputType::GetValueMissingMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
     "FormValidationValueMissing", aMessage);
 }
 
 nsresult
-InputType::GetTypeMismatchMessage(nsXPIDLString& aMessage)
+InputType::GetTypeMismatchMessage(nsAString& aMessage)
 {
   return NS_ERROR_UNEXPECTED;
 }
 
 nsresult
-InputType::GetRangeOverflowMessage(nsXPIDLString& aMessage)
+InputType::GetRangeOverflowMessage(nsAString& aMessage)
 {
   return NS_ERROR_UNEXPECTED;
 }
 
 nsresult
-InputType::GetRangeUnderflowMessage(nsXPIDLString& aMessage)
+InputType::GetRangeUnderflowMessage(nsAString& aMessage)
 {
   return NS_ERROR_UNEXPECTED;
 }
 
 nsresult
-InputType::GetBadInputMessage(nsXPIDLString& aMessage)
+InputType::GetBadInputMessage(nsAString& aMessage)
 {
   return NS_ERROR_UNEXPECTED;
 }
diff --git a/dom/html/input/InputType.h b/dom/html/input/InputType.h
index 3836f67feef9..bf49bc35efbe 100644
--- a/dom/html/input/InputType.h
+++ b/dom/html/input/InputType.h
@@ -63,11 +63,11 @@ public:
 
   nsresult GetValidationMessage(nsAString& aValidationMessage,
                                 nsIConstraintValidation::ValidityStateType aType);
-  virtual nsresult GetValueMissingMessage(nsXPIDLString& aMessage);
-  virtual nsresult GetTypeMismatchMessage(nsXPIDLString& aMessage);
-  virtual nsresult GetRangeOverflowMessage(nsXPIDLString& aMessage);
-  virtual nsresult GetRangeUnderflowMessage(nsXPIDLString& aMessage);
-  virtual nsresult GetBadInputMessage(nsXPIDLString& aMessage);
+  virtual nsresult GetValueMissingMessage(nsAString& aMessage);
+  virtual nsresult GetTypeMismatchMessage(nsAString& aMessage);
+  virtual nsresult GetRangeOverflowMessage(nsAString& aMessage);
+  virtual nsresult GetRangeUnderflowMessage(nsAString& aMessage);
+  virtual nsresult GetBadInputMessage(nsAString& aMessage);
 
   virtual nsresult MinMaxStepAttrChanged();
 
diff --git a/dom/html/input/NumericInputTypes.cpp b/dom/html/input/NumericInputTypes.cpp
index 3d821719cd32..a3706d9487a7 100644
--- a/dom/html/input/NumericInputTypes.cpp
+++ b/dom/html/input/NumericInputTypes.cpp
@@ -65,7 +65,7 @@ NumericInputTypeBase::HasStepMismatch(bool aUseZeroIfValueNaN) const
 }
 
 nsresult
-NumericInputTypeBase::GetRangeOverflowMessage(nsXPIDLString& aMessage)
+NumericInputTypeBase::GetRangeOverflowMessage(nsAString& aMessage)
 {
   // We want to show the value as parsed when it's a number
   mozilla::Decimal maximum = mInputElement->GetMaximum();
@@ -84,7 +84,7 @@ NumericInputTypeBase::GetRangeOverflowMessage(nsXPIDLString& aMessage)
 }
 
 nsresult
-NumericInputTypeBase::GetRangeUnderflowMessage(nsXPIDLString& aMessage)
+NumericInputTypeBase::GetRangeUnderflowMessage(nsAString& aMessage)
 {
   mozilla::Decimal minimum = mInputElement->GetMinimum();
   MOZ_ASSERT(!minimum.isNaN());
@@ -167,14 +167,14 @@ NumberInputType::HasBadInput() const
 }
 
 nsresult
-NumberInputType::GetValueMissingMessage(nsXPIDLString& aMessage)
+NumberInputType::GetValueMissingMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
     "FormValidationBadInputNumber", aMessage);
 }
 
 nsresult
-NumberInputType::GetBadInputMessage(nsXPIDLString& aMessage)
+NumberInputType::GetBadInputMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
     "FormValidationBadInputNumber", aMessage);
diff --git a/dom/html/input/NumericInputTypes.h b/dom/html/input/NumericInputTypes.h
index e8b272b59ed2..f9b2537e7e57 100644
--- a/dom/html/input/NumericInputTypes.h
+++ b/dom/html/input/NumericInputTypes.h
@@ -18,8 +18,8 @@ public:
   bool IsRangeUnderflow() const override;
   bool HasStepMismatch(bool aUseZeroIfValueNaN) const override;
 
-  nsresult GetRangeOverflowMessage(nsXPIDLString& aMessage) override;
-  nsresult GetRangeUnderflowMessage(nsXPIDLString& aMessage) override;
+  nsresult GetRangeOverflowMessage(nsAString& aMessage) override;
+  nsresult GetRangeUnderflowMessage(nsAString& aMessage) override;
 
   bool ConvertStringToNumber(nsAString& aValue,
                              mozilla::Decimal& aResultValue) const override;
@@ -45,8 +45,8 @@ public:
   bool IsValueMissing() const override;
   bool HasBadInput() const override;
 
-  nsresult GetValueMissingMessage(nsXPIDLString& aMessage) override;
-  nsresult GetBadInputMessage(nsXPIDLString& aMessage) override;
+  nsresult GetValueMissingMessage(nsAString& aMessage) override;
+  nsresult GetBadInputMessage(nsAString& aMessage) override;
 
 protected:
   bool IsMutable() const override;
diff --git a/dom/html/input/SingleLineTextInputTypes.cpp b/dom/html/input/SingleLineTextInputTypes.cpp
index 31f0eeed1dee..758594742f6e 100644
--- a/dom/html/input/SingleLineTextInputTypes.cpp
+++ b/dom/html/input/SingleLineTextInputTypes.cpp
@@ -121,7 +121,7 @@ URLInputType::HasTypeMismatch() const
 }
 
 nsresult
-URLInputType::GetTypeMismatchMessage(nsXPIDLString& aMessage)
+URLInputType::GetTypeMismatchMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                             "FormValidationInvalidURL",
@@ -165,7 +165,7 @@ EmailInputType::HasBadInput() const
 }
 
 nsresult
-EmailInputType::GetTypeMismatchMessage(nsXPIDLString& aMessage)
+EmailInputType::GetTypeMismatchMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                             "FormValidationInvalidEmail",
@@ -173,7 +173,7 @@ EmailInputType::GetTypeMismatchMessage(nsXPIDLString& aMessage)
 }
 
 nsresult
-EmailInputType::GetBadInputMessage(nsXPIDLString& aMessage)
+EmailInputType::GetBadInputMessage(nsAString& aMessage)
 {
   return nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                             "FormValidationInvalidEmail",
diff --git a/dom/html/input/SingleLineTextInputTypes.h b/dom/html/input/SingleLineTextInputTypes.h
index f2708cb3cd79..df2943c405af 100644
--- a/dom/html/input/SingleLineTextInputTypes.h
+++ b/dom/html/input/SingleLineTextInputTypes.h
@@ -88,7 +88,7 @@ public:
 
   bool HasTypeMismatch() const override;
 
-  nsresult GetTypeMismatchMessage(nsXPIDLString& aMessage) override;
+  nsresult GetTypeMismatchMessage(nsAString& aMessage) override;
 
 private:
   explicit URLInputType(mozilla::dom::HTMLInputElement* aInputElement)
@@ -109,8 +109,8 @@ public:
   bool HasTypeMismatch() const override;
   bool HasBadInput() const override;
 
-  nsresult GetTypeMismatchMessage(nsXPIDLString& aMessage) override;
-  nsresult GetBadInputMessage(nsXPIDLString& aMessage) override;
+  nsresult GetTypeMismatchMessage(nsAString& aMessage) override;
+  nsresult GetBadInputMessage(nsAString& aMessage) override;
 
 private:
   explicit EmailInputType(mozilla::dom::HTMLInputElement* aInputElement)
diff --git a/dom/html/nsHTMLDocument.cpp b/dom/html/nsHTMLDocument.cpp
index b7f094d7f7c8..e0c5c9491a3d 100644
--- a/dom/html/nsHTMLDocument.cpp
+++ b/dom/html/nsHTMLDocument.cpp
@@ -808,9 +808,9 @@ nsHTMLDocument::StartDocumentLoad(const char* aCommand,
     rv = bundleService->CreateBundle("chrome://global/locale/browser.properties",
                                      getter_AddRefs(bundle));
     NS_ASSERTION(NS_SUCCEEDED(rv) && bundle, "chrome://global/locale/browser.properties could not be loaded");
-    nsXPIDLString title;
+    nsAutoString title;
     if (bundle) {
-      bundle->GetStringFromName("plainText.wordWrap", getter_Copies(title));
+      bundle->GetStringFromName("plainText.wordWrap", title);
     }
     SetSelectedStyleSheetSet(title);
   }
diff --git a/dom/indexedDB/ScriptErrorHelper.cpp b/dom/indexedDB/ScriptErrorHelper.cpp
index 7d8efabfdd0f..ba774701ee7c 100644
--- a/dom/indexedDB/ScriptErrorHelper.cpp
+++ b/dom/indexedDB/ScriptErrorHelper.cpp
@@ -81,7 +81,7 @@ public:
     MOZ_ASSERT(NS_IsMainThread());
     MOZ_ASSERT(!aMessageName.IsEmpty());
 
-    nsXPIDLString localizedMessage;
+    nsAutoString localizedMessage;
     if (NS_WARN_IF(NS_FAILED(
       nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                          aMessageName.BeginReading(),
diff --git a/dom/media/CubebUtils.cpp b/dom/media/CubebUtils.cpp
index 99091b0dc575..2697e5f4275e 100644
--- a/dom/media/CubebUtils.cpp
+++ b/dom/media/CubebUtils.cpp
@@ -307,7 +307,7 @@ void InitBrandName()
   if (sBrandName) {
     return;
   }
-  nsXPIDLString brandName;
+  nsAutoString brandName;
   nsCOMPtr<nsIStringBundleService> stringBundleService =
     mozilla::services::GetStringBundleService();
   if (stringBundleService) {
@@ -315,8 +315,7 @@ void InitBrandName()
     nsresult rv = stringBundleService->CreateBundle(kBrandBundleURL,
                                            getter_AddRefs(brandBundle));
     if (NS_SUCCEEDED(rv)) {
-      rv = brandBundle->GetStringFromName("brandShortName",
-                                          getter_Copies(brandName));
+      rv = brandBundle->GetStringFromName("brandShortName", brandName);
       NS_WARNING_ASSERTION(
         NS_SUCCEEDED(rv), "Could not get the program name for a cubeb stream.");
     }
diff --git a/dom/media/webaudio/WebAudioUtils.cpp b/dom/media/webaudio/WebAudioUtils.cpp
index 50297088a442..d1da782b39d4 100644
--- a/dom/media/webaudio/WebAudioUtils.cpp
+++ b/dom/media/webaudio/WebAudioUtils.cpp
@@ -130,7 +130,7 @@ WebAudioUtils::LogToDeveloperConsole(uint64_t aWindowID, const char* aKey)
     return;
   }
 
-  nsXPIDLString result;
+  nsAutoString result;
   rv = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                           aKey, result);
 
diff --git a/dom/plugins/ipc/PluginHangUIParent.cpp b/dom/plugins/ipc/PluginHangUIParent.cpp
index 51861b8b9079..3a685de3533a 100644
--- a/dom/plugins/ipc/PluginHangUIParent.cpp
+++ b/dom/plugins/ipc/PluginHangUIParent.cpp
@@ -155,7 +155,7 @@ PluginHangUIParent::Init(const nsString& aPluginName)
   exePath = exePath.AppendASCII(MOZ_HANGUI_PROCESS_NAME);
   CommandLine commandLine(exePath.value());
 
-  nsXPIDLString localizedStr;
+  nsAutoString localizedStr;
   const char16_t* formatParams[] = { aPluginName.get() };
   rv = nsContentUtils::FormatLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                              "PluginHangUIMessage",
diff --git a/dom/security/nsCSPContext.cpp b/dom/security/nsCSPContext.cpp
index c8e87262deb6..1ba188caf030 100644
--- a/dom/security/nsCSPContext.cpp
+++ b/dom/security/nsCSPContext.cpp
@@ -779,8 +779,8 @@ nsCSPContext::logToConsole(const char* aName,
 {
   // let's check if we have to queue up console messages
   if (mQueueUpMessages) {
-    nsXPIDLString msg;
-    CSP_GetLocalizedStr(aName, aParams, aParamsLength, getter_Copies(msg));
+    nsAutoString msg;
+    CSP_GetLocalizedStr(aName, aParams, aParamsLength, msg);
     ConsoleMsgQueueElem &elem = *mConsoleMsgQueue.AppendElement();
     elem.mMsg = msg;
     elem.mSourceName = PromiseFlatString(aSourceName);
diff --git a/dom/security/nsCSPUtils.cpp b/dom/security/nsCSPUtils.cpp
index 9fb18ade06d3..faeab4404543 100644
--- a/dom/security/nsCSPUtils.cpp
+++ b/dom/security/nsCSPUtils.cpp
@@ -91,7 +91,7 @@ void
 CSP_GetLocalizedStr(const char* aName,
                     const char16_t** aParams,
                     uint32_t aLength,
-                    char16_t** outResult)
+                    nsAString& outResult)
 {
   nsCOMPtr<nsIStringBundle> keyStringBundle;
   nsCOMPtr<nsIStringBundleService> stringBundleService =
@@ -193,8 +193,8 @@ CSP_LogLocalizedStr(const char* aName,
                     const char* aCategory,
                     uint64_t aInnerWindowID)
 {
-  nsXPIDLString logMsg;
-  CSP_GetLocalizedStr(aName, aParams, aLength, getter_Copies(logMsg));
+  nsAutoString logMsg;
+  CSP_GetLocalizedStr(aName, aParams, aLength, logMsg);
   CSP_LogMessage(logMsg, aSourceName, aSourceLine,
                  aLineNumber, aColumnNumber, aFlags,
                  aCategory, aInnerWindowID);
diff --git a/dom/security/nsCSPUtils.h b/dom/security/nsCSPUtils.h
index 0219071cf78d..fb92b991ae45 100644
--- a/dom/security/nsCSPUtils.h
+++ b/dom/security/nsCSPUtils.h
@@ -38,7 +38,7 @@ void CSP_LogLocalizedStr(const char* aName,
 void CSP_GetLocalizedStr(const char* aName,
                          const char16_t** aParams,
                          uint32_t aLength,
-                         char16_t** outResult);
+                         nsAString& outResult);
 
 void CSP_LogStrMessage(const nsAString& aMsg);
 
diff --git a/dom/webbrowserpersist/nsWebBrowserPersist.cpp b/dom/webbrowserpersist/nsWebBrowserPersist.cpp
index f9714f7471c6..ef02e58fc46d 100644
--- a/dom/webbrowserpersist/nsWebBrowserPersist.cpp
+++ b/dom/webbrowserpersist/nsWebBrowserPersist.cpp
@@ -1228,13 +1228,14 @@ nsresult nsWebBrowserPersist::SendErrorStatusChange(
     rv = s->CreateBundle(kWebBrowserPersistStringBundle, getter_AddRefs(bundle));
     NS_ENSURE_TRUE(NS_SUCCEEDED(rv) && bundle, NS_ERROR_FAILURE);
 
-    nsXPIDLString msgText;
+    nsAutoString msgText;
     const char16_t *strings[1];
     strings[0] = path.get();
-    rv = bundle->FormatStringFromName(msgId, strings, 1, getter_Copies(msgText));
+    rv = bundle->FormatStringFromName(msgId, strings, 1, msgText);
     NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
 
-    mProgressListener->OnStatusChange(nullptr, aRequest, aResult, msgText);
+    mProgressListener->OnStatusChange(nullptr, aRequest, aResult,
+                                      msgText.get());
 
     return NS_OK;
 }
diff --git a/dom/workers/ServiceWorkerManager.cpp b/dom/workers/ServiceWorkerManager.cpp
index a7c2fdaf5946..7bf60343e80f 100644
--- a/dom/workers/ServiceWorkerManager.cpp
+++ b/dom/workers/ServiceWorkerManager.cpp
@@ -1884,7 +1884,7 @@ ServiceWorkerManager::LocalizeAndReportToAllClients(
   }
 
   nsresult rv;
-  nsXPIDLString message;
+  nsAutoString message;
   rv = nsContentUtils::FormatLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                              aStringKey, aParamArray, message);
   if (NS_SUCCEEDED(rv)) {
diff --git a/dom/workers/ServiceWorkerUpdateJob.cpp b/dom/workers/ServiceWorkerUpdateJob.cpp
index a5d826b6e1bf..8eb2f00115cf 100644
--- a/dom/workers/ServiceWorkerUpdateJob.cpp
+++ b/dom/workers/ServiceWorkerUpdateJob.cpp
@@ -401,7 +401,7 @@ ServiceWorkerUpdateJob::ComparisonResult(nsresult aStatus,
   }
 
   if (!StringBeginsWith(mRegistration->mScope, maxPrefix)) {
-    nsXPIDLString message;
+    nsAutoString message;
     NS_ConvertUTF8toUTF16 reportScope(mRegistration->mScope);
     NS_ConvertUTF8toUTF16 reportMaxPrefix(maxPrefix);
     const char16_t* params[] = { reportScope.get(), reportMaxPrefix.get() };
diff --git a/dom/xslt/xslt/txMozillaXSLTProcessor.cpp b/dom/xslt/xslt/txMozillaXSLTProcessor.cpp
index bc554e54878e..83a4137283cb 100644
--- a/dom/xslt/xslt/txMozillaXSLTProcessor.cpp
+++ b/dom/xslt/xslt/txMozillaXSLTProcessor.cpp
@@ -1077,11 +1077,10 @@ txMozillaXSLTProcessor::reportError(nsresult aResult,
         nsCOMPtr<nsIStringBundleService> sbs =
             mozilla::services::GetStringBundleService();
         if (sbs) {
-            nsXPIDLString errorText;
-            sbs->FormatStatusMessage(aResult, EmptyString().get(),
-                                     getter_Copies(errorText));
+            nsAutoString errorText;
+            sbs->FormatStatusMessage(aResult, EmptyString().get(), errorText);
 
-            nsXPIDLString errorMessage;
+            nsAutoString errorMessage;
             nsCOMPtr<nsIStringBundle> bundle;
             sbs->CreateBundle(XSLT_MSGS_URL, getter_AddRefs(bundle));
 
@@ -1089,13 +1088,11 @@ txMozillaXSLTProcessor::reportError(nsresult aResult,
                 const char16_t* error[] = { errorText.get() };
                 if (mStylesheet) {
                     bundle->FormatStringFromName("TransformError",
-                                                 error, 1,
-                                                 getter_Copies(errorMessage));
+                                                 error, 1, errorMessage);
                 }
                 else {
                     bundle->FormatStringFromName("LoadingError",
-                                                 error, 1,
-                                                 getter_Copies(errorMessage));
+                                                 error, 1, errorMessage);
                 }
             }
             mErrorText.Assign(errorMessage);
diff --git a/extensions/pref/autoconfig/src/nsAutoConfig.cpp b/extensions/pref/autoconfig/src/nsAutoConfig.cpp
index e34321cf3d20..57a3c575a8d0 100644
--- a/extensions/pref/autoconfig/src/nsAutoConfig.cpp
+++ b/extensions/pref/autoconfig/src/nsAutoConfig.cpp
@@ -518,12 +518,12 @@ nsresult nsAutoConfig::PromptForEMailAddress(nsACString &emailAddress)
                                 getter_AddRefs(bundle));
     NS_ENSURE_SUCCESS(rv, rv);
 
-    nsXPIDLString title;
-    rv = bundle->GetStringFromName("emailPromptTitle", getter_Copies(title));
+    nsAutoString title;
+    rv = bundle->GetStringFromName("emailPromptTitle", title);
     NS_ENSURE_SUCCESS(rv, rv);
 
-    nsXPIDLString err;
-    rv = bundle->GetStringFromName("emailPromptMsg", getter_Copies(err));
+    nsAutoString err;
+    rv = bundle->GetStringFromName("emailPromptMsg", err);
     NS_ENSURE_SUCCESS(rv, rv);
     bool check = false;
     nsXPIDLString emailResult;
diff --git a/extensions/pref/autoconfig/src/nsReadConfig.cpp b/extensions/pref/autoconfig/src/nsReadConfig.cpp
index be1c0b3c79d3..bf77d7019ec0 100644
--- a/extensions/pref/autoconfig/src/nsReadConfig.cpp
+++ b/extensions/pref/autoconfig/src/nsReadConfig.cpp
@@ -54,13 +54,13 @@ static void DisplayError(void)
     if (!bundle)
         return;
 
-    nsXPIDLString title;
-    rv = bundle->GetStringFromName("readConfigTitle", getter_Copies(title));
+    nsAutoString title;
+    rv = bundle->GetStringFromName("readConfigTitle", title);
     if (NS_FAILED(rv))
         return;
 
-    nsXPIDLString err;
-    rv = bundle->GetStringFromName("readConfigMsg", getter_Copies(err));
+    nsAutoString err;
+    rv = bundle->GetStringFromName("readConfigMsg", err);
     if (NS_FAILED(rv))
         return;
 
diff --git a/gfx/layers/ImageContainer.h b/gfx/layers/ImageContainer.h
index 86110b3e23be..3b5c91d128f0 100644
--- a/gfx/layers/ImageContainer.h
+++ b/gfx/layers/ImageContainer.h
@@ -543,6 +543,9 @@ public:
   void SetScaleHint(const gfx::IntSize& aScaleHint)
   { mScaleHint = aScaleHint; }
 
+  const gfx::IntSize& GetScaleHint() const
+  { return mScaleHint; }
+
   void SetImageFactory(ImageFactory *aFactory)
   {
     RecursiveMutexAutoLock lock(mRecursiveMutex);
diff --git a/gfx/layers/wr/WebRenderLayerManager.cpp b/gfx/layers/wr/WebRenderLayerManager.cpp
index 459f1314d2b4..bd98b1f81372 100644
--- a/gfx/layers/wr/WebRenderLayerManager.cpp
+++ b/gfx/layers/wr/WebRenderLayerManager.cpp
@@ -320,13 +320,17 @@ WebRenderLayerManager::CreateImageKey(nsDisplayItem* aItem,
       LayoutDeviceRect::FromAppUnits(bounds, appUnitsPerDevPixel),
       PixelCastJustification::WebRenderHasUnitResolution);
     LayerRect scBounds(0, 0, rect.width, rect.height);
+    MaybeIntSize scaleToSize;
+    if (!aContainer->GetScaleHint().IsEmpty()) {
+      scaleToSize = Some(aContainer->GetScaleHint());
+    }
     imageData->CreateAsyncImageWebRenderCommands(aBuilder,
                                                  aContainer,
                                                  aSc,
                                                  rect,
                                                  scBounds,
                                                  gfx::Matrix4x4(),
-                                                 Nothing(),
+                                                 scaleToSize,
                                                  wr::ImageRendering::Auto,
                                                  wr::MixBlendMode::Normal);
     return Nothing();
@@ -351,6 +355,11 @@ WebRenderLayerManager::PushImage(nsDisplayItem* aItem,
 {
   gfx::IntSize size;
   Maybe<wr::ImageKey> key = CreateImageKey(aItem, aContainer, aBuilder, aSc, size);
+  if (aContainer->IsAsync()) {
+    // Async ImageContainer does not create ImageKey, instead it uses Pipeline.
+    MOZ_ASSERT(key.isNothing());
+    return true;
+  }
   if (!key) {
     return false;
   }
diff --git a/intl/strres/nsIStringBundle.idl b/intl/strres/nsIStringBundle.idl
index 3383f39ce6dc..123bcb198b87 100644
--- a/intl/strres/nsIStringBundle.idl
+++ b/intl/strres/nsIStringBundle.idl
@@ -16,42 +16,35 @@
 
 #define NS_STRINGBUNDLE_CONTRACTID "@mozilla.org/intl/stringbundle;1"
 
-/** 
- * observer needs to check if the bundle handle matches
- */
-#define NS_STRBUNDLE_LOADED_TOPIC "strbundle-loaded"
-
 %}
 
-native nsStrBundleLoadedFunc(nsStrBundleLoadedFunc);
-
 [scriptable, uuid(D85A17C2-AA7C-11d2-9B8C-00805F8A16D9)]
 interface nsIStringBundle : nsISupports
 {
-  wstring GetStringFromID(in long aID);
+  AString GetStringFromID(in long aID);
 
   // This method is mostly used from JS, where AUTF8String is appropriate.
   [binaryname(GetStringFromAUTF8Name)]
-  wstring GetStringFromName(in AUTF8String aName);
+  AString GetStringFromName(in AUTF8String aName);
 
   // This method is mostly used from C++, where |string| is appropriate because
   // the names are most often 8-bit string literals (normally ASCII, though
   // u8"foo" literals will also work).
   [noscript, binaryname(GetStringFromName)]
-  wstring GetStringFromNameCpp(in string aName);
+  AString GetStringFromNameCpp(in string aName);
 
   // this is kind of like smprintf - except that you can
   // only pass it unicode strings, using the %S formatting character.
   // the id or name should refer to a string in the bundle that
   // uses %S.. do NOT try to use any other types.
   // this uses nsTextFormatter::smprintf to do the dirty work.
-  wstring formatStringFromID(in long aID,
+  AString formatStringFromID(in long aID,
                              [array, size_is(length)] in wstring params,
                              in unsigned long length);
 
   // This method is mostly used from JS, where AUTF8String is appropriate.
   [binaryname(FormatStringFromAUTF8Name)]
-  wstring formatStringFromName(in AUTF8String aName,
+  AString formatStringFromName(in AUTF8String aName,
                                [array, size_is(length)] in wstring params,
                                in unsigned long length);
 
@@ -59,7 +52,7 @@ interface nsIStringBundle : nsISupports
   // the names are most often 8-bit string literals (normally ASCII, though
   // u8"foo" literals will also work).
   [noscript, binaryname(FormatStringFromName)]
-  wstring formatStringFromNameCpp(in string aName,
+  AString formatStringFromNameCpp(in string aName,
                                   [array, size_is(length)] in wstring params,
                                   in unsigned long length);
 
@@ -67,7 +60,6 @@ interface nsIStringBundle : nsISupports
   Implements nsISimpleEnumerator, replaces nsIEnumerator 
   */
   nsISimpleEnumerator getSimpleEnumeration();
-
 };
 
 [scriptable, uuid(D85A17C0-AA7C-11d2-9B8C-00805F8A16D9)]
@@ -84,7 +76,7 @@ interface nsIStringBundleService : nsISupports
    *            can be separated by newline ('\n') characters.
    * @return the formatted message
    */
-  wstring formatStatusMessage(in nsresult aStatus, in wstring aStatusArg);
+  AString formatStatusMessage(in nsresult aStatus, in wstring aStatusArg);
 
   /**
    * flushes the string bundle cache - useful when the locale changes or
diff --git a/intl/strres/nsStringBundle.cpp b/intl/strres/nsStringBundle.cpp
index 41e127b446bc..bf6a10db9df2 100644
--- a/intl/strres/nsStringBundle.cpp
+++ b/intl/strres/nsStringBundle.cpp
@@ -115,8 +115,23 @@ nsStringBundle::LoadProperties()
   return rv;
 }
 
-nsresult
-nsStringBundle::GetStringFromNameHelper(const char* aName, nsAString& aResult)
+NS_IMETHODIMP
+nsStringBundle::GetStringFromID(int32_t aID, nsAString& aResult)
+{
+  nsAutoCString idStr;
+  idStr.AppendInt(aID, 10);
+  return GetStringFromName(idStr.get(), aResult);
+}
+
+NS_IMETHODIMP
+nsStringBundle::GetStringFromAUTF8Name(const nsACString& aName,
+                                       nsAString& aResult)
+{
+  return GetStringFromName(PromiseFlatCString(aName).get(), aResult);
+}
+
+NS_IMETHODIMP
+nsStringBundle::GetStringFromName(const char* aName, nsAString& aResult)
 {
   NS_ENSURE_ARG_POINTER(aName);
 
@@ -133,47 +148,14 @@ nsStringBundle::GetStringFromNameHelper(const char* aName, nsAString& aResult)
     if (NS_SUCCEEDED(rv)) return rv;
   }
 
-  rv = mProps->GetStringProperty(nsDependentCString(aName), aResult);
-  return rv;
-}
-
-NS_IMETHODIMP
-nsStringBundle::GetStringFromID(int32_t aID, char16_t **aResult)
-{
-  nsAutoCString idStr;
-  idStr.AppendInt(aID, 10);
-  return GetStringFromName(idStr.get(), aResult);
-}
-
-NS_IMETHODIMP
-nsStringBundle::GetStringFromAUTF8Name(const nsACString& aName,
-                                       char16_t **aResult)
-{
-  return GetStringFromName(PromiseFlatCString(aName).get(), aResult);
-}
-
-NS_IMETHODIMP
-nsStringBundle::GetStringFromName(const char* aName, char16_t** aResult)
-{
-  NS_ENSURE_ARG_POINTER(aResult);
-
-  *aResult = nullptr;
-
-  nsAutoString tmpstr;
-  nsresult rv = GetStringFromNameHelper(aName, tmpstr);
-  if (NS_FAILED(rv)) return rv;
-
-  *aResult = ToNewUnicode(tmpstr);
-  NS_ENSURE_TRUE(*aResult, NS_ERROR_OUT_OF_MEMORY);
-
-  return NS_OK;
+  return mProps->GetStringProperty(nsDependentCString(aName), aResult);
 }
 
 NS_IMETHODIMP
 nsStringBundle::FormatStringFromID(int32_t aID,
                                    const char16_t **aParams,
                                    uint32_t aLength,
-                                   char16_t ** aResult)
+                                   nsAString& aResult)
 {
   nsAutoCString idStr;
   idStr.AppendInt(aID, 10);
@@ -185,7 +167,7 @@ NS_IMETHODIMP
 nsStringBundle::FormatStringFromAUTF8Name(const nsACString& aName,
                                           const char16_t **aParams,
                                           uint32_t aLength,
-                                          char16_t **aResult)
+                                          nsAString& aResult)
 {
   return FormatStringFromName(PromiseFlatCString(aName).get(), aParams,
                               aLength, aResult);
@@ -196,15 +178,12 @@ NS_IMETHODIMP
 nsStringBundle::FormatStringFromName(const char* aName,
                                      const char16_t** aParams,
                                      uint32_t aLength,
-                                     char16_t** aResult)
+                                     nsAString& aResult)
 {
-  NS_ENSURE_ARG_POINTER(aResult);
   NS_ASSERTION(aParams && aLength, "FormatStringFromName() without format parameters: use GetStringFromName() instead");
 
-  *aResult = nullptr;
-
   nsAutoString formatStr;
-  nsresult rv = GetStringFromNameHelper(aName, formatStr);
+  nsresult rv = GetStringFromName(aName, formatStr);
   if (NS_FAILED(rv)) return rv;
 
   return FormatString(formatStr.get(), aParams, aLength, aResult);
@@ -294,9 +273,8 @@ nsStringBundle::GetSimpleEnumeration(nsISimpleEnumerator** elements)
 nsresult
 nsStringBundle::FormatString(const char16_t *aFormatStr,
                              const char16_t **aParams, uint32_t aLength,
-                             char16_t **aResult)
+                             nsAString& aResult)
 {
-  NS_ENSURE_ARG_POINTER(aResult);
   NS_ENSURE_ARG(aLength <= 10); // enforce 10-parameter limit
 
   // implementation note: you would think you could use vsmprintf
@@ -305,20 +283,19 @@ nsStringBundle::FormatString(const char16_t *aFormatStr,
   // Don't believe me? See:
   //   http://www.eskimo.com/~scs/C-faq/q15.13.html
   // -alecf
-  *aResult =
-    nsTextFormatter::smprintf(aFormatStr,
-                              aLength >= 1 ? aParams[0] : nullptr,
-                              aLength >= 2 ? aParams[1] : nullptr,
-                              aLength >= 3 ? aParams[2] : nullptr,
-                              aLength >= 4 ? aParams[3] : nullptr,
-                              aLength >= 5 ? aParams[4] : nullptr,
-                              aLength >= 6 ? aParams[5] : nullptr,
-                              aLength >= 7 ? aParams[6] : nullptr,
-                              aLength >= 8 ? aParams[7] : nullptr,
-                              aLength >= 9 ? aParams[8] : nullptr,
-                              aLength >= 10 ? aParams[9] : nullptr);
+  nsTextFormatter::ssprintf(aResult, aFormatStr,
+                            aLength >= 1 ? aParams[0] : nullptr,
+                            aLength >= 2 ? aParams[1] : nullptr,
+                            aLength >= 3 ? aParams[2] : nullptr,
+                            aLength >= 4 ? aParams[3] : nullptr,
+                            aLength >= 5 ? aParams[4] : nullptr,
+                            aLength >= 6 ? aParams[5] : nullptr,
+                            aLength >= 7 ? aParams[6] : nullptr,
+                            aLength >= 8 ? aParams[7] : nullptr,
+                            aLength >= 9 ? aParams[8] : nullptr,
+                            aLength >= 10 ? aParams[9] : nullptr);
 
-  return *aResult ? NS_OK : NS_ERROR_OUT_OF_MEMORY;
+  return NS_OK;
 }
 
 NS_IMPL_ISUPPORTS(nsExtensibleStringBundle, nsIStringBundle)
@@ -373,21 +350,24 @@ nsExtensibleStringBundle::~nsExtensibleStringBundle()
 {
 }
 
-nsresult nsExtensibleStringBundle::GetStringFromID(int32_t aID, char16_t ** aResult)
+nsresult
+nsExtensibleStringBundle::GetStringFromID(int32_t aID, nsAString& aResult)
 {
   nsAutoCString idStr;
   idStr.AppendInt(aID, 10);
   return GetStringFromName(idStr.get(), aResult);
 }
 
-nsresult nsExtensibleStringBundle::GetStringFromAUTF8Name(
-  const nsACString& aName, char16_t ** aResult)
+nsresult
+nsExtensibleStringBundle::GetStringFromAUTF8Name(const nsACString& aName,
+                                                 nsAString& aResult)
 {
   return GetStringFromName(PromiseFlatCString(aName).get(), aResult);
 }
 
-nsresult nsExtensibleStringBundle::GetStringFromName(const char* aName,
-                                                     char16_t** aResult)
+nsresult
+nsExtensibleStringBundle::GetStringFromName(const char* aName,
+                                            nsAString& aResult)
 {
   nsresult rv;
   const uint32_t size = mBundles.Count();
@@ -407,7 +387,7 @@ NS_IMETHODIMP
 nsExtensibleStringBundle::FormatStringFromID(int32_t aID,
                                              const char16_t ** aParams,
                                              uint32_t aLength,
-                                             char16_t ** aResult)
+                                             nsAString& aResult)
 {
   nsAutoCString idStr;
   idStr.AppendInt(aID, 10);
@@ -418,7 +398,7 @@ NS_IMETHODIMP
 nsExtensibleStringBundle::FormatStringFromAUTF8Name(const nsACString& aName,
                                                     const char16_t ** aParams,
                                                     uint32_t aLength,
-                                                    char16_t ** aResult)
+                                                    nsAString& aResult)
 {
   return FormatStringFromName(PromiseFlatCString(aName).get(),
                               aParams, aLength, aResult);
@@ -428,15 +408,16 @@ NS_IMETHODIMP
 nsExtensibleStringBundle::FormatStringFromName(const char* aName,
                                                const char16_t** aParams,
                                                uint32_t aLength,
-                                               char16_t** aResult)
+                                               nsAString& aResult)
 {
-  nsXPIDLString formatStr;
+  nsAutoString formatStr;
   nsresult rv;
-  rv = GetStringFromName(aName, getter_Copies(formatStr));
+  rv = GetStringFromName(aName, formatStr);
   if (NS_FAILED(rv))
     return rv;
 
-  return nsStringBundle::FormatString(formatStr, aParams, aLength, aResult);
+  return nsStringBundle::FormatString(formatStr.get(), aParams, aLength,
+                                      aResult);
 }
 
 nsresult nsExtensibleStringBundle::GetSimpleEnumeration(nsISimpleEnumerator ** aResult)
@@ -635,7 +616,7 @@ nsStringBundleService::CreateExtensibleBundle(const char* aCategory,
 nsresult
 nsStringBundleService::FormatWithBundle(nsIStringBundle* bundle, nsresult aStatus,
                                         uint32_t argCount, char16_t** argArray,
-                                        char16_t* *result)
+                                        nsAString& result)
 {
   nsresult rv;
   nsXPIDLCString key;
@@ -661,7 +642,7 @@ nsStringBundleService::FormatWithBundle(nsIStringBundle* bundle, nsresult aStatu
 NS_IMETHODIMP
 nsStringBundleService::FormatStatusMessage(nsresult aStatus,
                                            const char16_t* aStatusArg,
-                                           char16_t* *result)
+                                           nsAString& result)
 {
   nsresult rv;
   uint32_t i, argCount = 0;
@@ -670,8 +651,7 @@ nsStringBundleService::FormatStatusMessage(nsresult aStatus,
 
   // XXX hack for mailnews who has already formatted their messages:
   if (aStatus == NS_OK && aStatusArg) {
-    *result = NS_strdup(aStatusArg);
-    NS_ENSURE_TRUE(*result, NS_ERROR_OUT_OF_MEMORY);
+    result.Assign(aStatusArg);
     return NS_OK;
   }
 
diff --git a/intl/strres/nsStringBundle.h b/intl/strres/nsStringBundle.h
index 68ef64b784b9..2b9b7cd96741 100644
--- a/intl/strres/nsStringBundle.h
+++ b/intl/strres/nsStringBundle.h
@@ -30,8 +30,6 @@ public:
 protected:
     virtual ~nsStringBundle();
 
-    nsresult GetStringFromNameHelper(const char* aName, nsAString& aResult);
-
     nsresult GetCombinedEnumeration(nsIStringBundleOverride* aOverrideString,
                                     nsISimpleEnumerator** aResult);
 private:
@@ -44,7 +42,7 @@ private:
 public:
     static nsresult FormatString(const char16_t *formatStr,
                                  const char16_t **aParams, uint32_t aLength,
-                                 char16_t **aResult);
+                                 nsAString& aResult);
 };
 
 class nsExtensibleStringBundle;
diff --git a/intl/strres/nsStringBundleService.h b/intl/strres/nsStringBundleService.h
index 547cfe44d9d4..8763d6d81578 100644
--- a/intl/strres/nsStringBundleService.h
+++ b/intl/strres/nsStringBundleService.h
@@ -39,7 +39,7 @@ private:
   void getStringBundle(const char *aUrl, nsIStringBundle** aResult);
   nsresult FormatWithBundle(nsIStringBundle* bundle, nsresult aStatus,
                             uint32_t argCount, char16_t** argArray,
-                            char16_t* *result);
+                            nsAString& result);
 
   void flushBundleCache();
 
diff --git a/layout/base/nsCSSFrameConstructor.cpp b/layout/base/nsCSSFrameConstructor.cpp
index c22439d90ea0..ad108b8f9aad 100644
--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -1837,7 +1837,7 @@ nsCSSFrameConstructor::CreateGeneratedContent(nsFrameConstructorState& aState,
           return content.forget();
         }
 
-        nsXPIDLString temp;
+        nsAutoString temp;
         nsContentUtils::GetLocalizedString(nsContentUtils::eFORMS_PROPERTIES,
                                            "Submit", temp);
         return CreateGenConTextNode(aState, temp, nullptr, nullptr);
@@ -9129,9 +9129,9 @@ nsCSSFrameConstructor::WillDestroyFrameTree()
 // XXXbz I'd really like this method to go away. Once we have inline-block and
 // I can just use that for sized broken images, that can happen, maybe.
 void
-nsCSSFrameConstructor::GetAlternateTextFor(nsIContent*    aContent,
-                                           nsIAtom*       aTag,
-                                           nsXPIDLString& aAltText)
+nsCSSFrameConstructor::GetAlternateTextFor(nsIContent* aContent,
+                                           nsIAtom* aTag,
+                                           nsAString& aAltText)
 {
   // The "alt" attribute specifies alternate text that is rendered
   // when the image can not be displayed.
diff --git a/layout/base/nsCSSFrameConstructor.h b/layout/base/nsCSSFrameConstructor.h
index 9d0ff450ff40..ceb92dc0ad18 100644
--- a/layout/base/nsCSSFrameConstructor.h
+++ b/layout/base/nsCSSFrameConstructor.h
@@ -65,9 +65,9 @@ public:
   }
 
   // get the alternate text for a content node
-  static void GetAlternateTextFor(nsIContent*    aContent,
-                                  nsIAtom*       aTag,  // content object's tag
-                                  nsXPIDLString& aAltText);
+  static void GetAlternateTextFor(nsIContent* aContent,
+                                  nsIAtom* aTag,  // content object's tag
+                                  nsAString& aAltText);
 
 private:
   nsCSSFrameConstructor(const nsCSSFrameConstructor& aCopy) = delete;
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index c08f21207cc2..e5d737d7ebb0 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -1268,7 +1268,7 @@ nsDocumentViewer::PermitUnloadInternal(bool *aShouldPrompt,
                                      isTabModalPromptAllowed);
       }
 
-      nsXPIDLString title, message, stayLabel, leaveLabel;
+      nsAutoString title, message, stayLabel, leaveLabel;
       rv  = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
                                                "OnBeforeUnloadTitle",
                                                title);
@@ -1291,7 +1291,7 @@ nsDocumentViewer::PermitUnloadInternal(bool *aShouldPrompt,
         rv = tmp;
       }
 
-      if (NS_FAILED(rv) || !title || !message || !stayLabel || !leaveLabel) {
+      if (NS_FAILED(rv)) {
         NS_ERROR("Failed to get strings from dom.properties!");
         return NS_OK;
       }
@@ -1307,9 +1307,9 @@ nsDocumentViewer::PermitUnloadInternal(bool *aShouldPrompt,
       nsAutoSyncOperation sync(mDocument);
       mInPermitUnloadPrompt = true;
       mozilla::Telemetry::Accumulate(mozilla::Telemetry::ONBEFOREUNLOAD_PROMPT_COUNT, 1);
-      rv = prompt->ConfirmEx(title, message, buttonFlags,
-                             leaveLabel, stayLabel, nullptr, nullptr,
-                             &dummy, &buttonPressed);
+      rv = prompt->ConfirmEx(title.get(), message.get(), buttonFlags,
+                             leaveLabel.get(), stayLabel.get(),
+                             nullptr, nullptr, &dummy, &buttonPressed);
       mInPermitUnloadPrompt = false;
 
       // If the prompt aborted, we tell our consumer that it is not allowed
diff --git a/layout/forms/nsFileControlFrame.cpp b/layout/forms/nsFileControlFrame.cpp
index f6ed555b0332..323698e85dc5 100644
--- a/layout/forms/nsFileControlFrame.cpp
+++ b/layout/forms/nsFileControlFrame.cpp
@@ -88,7 +88,7 @@ MakeAnonButton(nsIDocument* aDoc, const char* labelKey,
                   NS_LITERAL_STRING("button"), false);
 
   // Set the file picking button text depending on the current locale.
-  nsXPIDLString buttonTxt;
+  nsAutoString buttonTxt;
   nsContentUtils::GetLocalizedString(nsContentUtils::eFORMS_PROPERTIES,
                                      labelKey, buttonTxt);
 
diff --git a/layout/generic/DetailsFrame.cpp b/layout/generic/DetailsFrame.cpp
index 6054aefffdf2..f536c3eb4850 100644
--- a/layout/generic/DetailsFrame.cpp
+++ b/layout/generic/DetailsFrame.cpp
@@ -105,7 +105,7 @@ DetailsFrame::CreateAnonymousContent(nsTArray<ContentInfo>& aElements)
                                  nsIDOMNode::ELEMENT_NODE);
   mDefaultSummary = new HTMLSummaryElement(nodeInfo);
 
-  nsXPIDLString defaultSummaryText;
+  nsAutoString defaultSummaryText;
   nsContentUtils::GetLocalizedString(nsContentUtils::eFORMS_PROPERTIES,
                                      "DefaultSummary", defaultSummaryText);
   RefPtr<nsTextNode> description = new nsTextNode(nodeInfoManager);
diff --git a/layout/generic/nsImageFrame.cpp b/layout/generic/nsImageFrame.cpp
index c51ce9c4b47f..cde3985eca74 100644
--- a/layout/generic/nsImageFrame.cpp
+++ b/layout/generic/nsImageFrame.cpp
@@ -1498,7 +1498,7 @@ nsImageFrame::DisplayAltFeedback(gfxContext& aRenderingContext,
   if (!inner.IsEmpty()) {
     nsIContent* content = GetContent();
     if (content) {
-      nsXPIDLString altText;
+      nsAutoString altText;
       nsCSSFrameConstructor::GetAlternateTextFor(content,
                                                  content->NodeInfo()->NameAtom(),
                                                  altText);
diff --git a/layout/generic/nsSimplePageSequenceFrame.cpp b/layout/generic/nsSimplePageSequenceFrame.cpp
index cb47887fa8a4..b2619a090dda 100644
--- a/layout/generic/nsSimplePageSequenceFrame.cpp
+++ b/layout/generic/nsSimplePageSequenceFrame.cpp
@@ -393,7 +393,7 @@ void
 nsSimplePageSequenceFrame::SetPageNumberFormat(const char* aPropName, const char* aDefPropVal, bool aPageNumOnly)
 {
   // Doing this here so we only have to go get these formats once
-  nsXPIDLString pageNumberFormat;
+  nsAutoString pageNumberFormat;
   // Now go get the Localized Page Formating String
   nsresult rv =
     nsContentUtils::GetLocalizedString(nsContentUtils::ePRINTING_PROPERTIES,
diff --git a/layout/printing/nsPrintData.cpp b/layout/printing/nsPrintData.cpp
index 9565de4a769b..6ce869851591 100644
--- a/layout/printing/nsPrintData.cpp
+++ b/layout/printing/nsPrintData.cpp
@@ -41,7 +41,6 @@ nsPrintData::nsPrintData(ePrintDataType aType)
   , mShrinkRatio(1.0)
   , mOrigDCScale(1.0)
   , mPPEventListeners(nullptr)
-  , mBrandName(nullptr)
 {
   nsCOMPtr<nsIStringBundle> brandBundle;
   nsCOMPtr<nsIStringBundleService> svc =
@@ -49,14 +48,13 @@ nsPrintData::nsPrintData(ePrintDataType aType)
   if (svc) {
     svc->CreateBundle( "chrome://branding/locale/brand.properties", getter_AddRefs( brandBundle ) );
     if (brandBundle) {
-      brandBundle->GetStringFromName("brandShortName", &mBrandName );
+      brandBundle->GetStringFromName("brandShortName", mBrandName);
     }
   }
 
-  if (!mBrandName) {
-    mBrandName = ToNewUnicode(NS_LITERAL_STRING("Mozilla Document"));
+  if (mBrandName.IsEmpty()) {
+    mBrandName.AssignLiteral(u"Mozilla Document");
   }
-
 }
 
 nsPrintData::~nsPrintData()
@@ -91,10 +89,6 @@ nsPrintData::~nsPrintData()
       }
     }
   }
-
-  if (mBrandName) {
-    free(mBrandName);
-  }
 }
 
 void nsPrintData::OnStartPrinting()
diff --git a/layout/printing/nsPrintData.h b/layout/printing/nsPrintData.h
index a6b09d0c5b8d..fe54070d419c 100644
--- a/layout/printing/nsPrintData.h
+++ b/layout/printing/nsPrintData.h
@@ -87,7 +87,7 @@ public:
   nsCOMPtr<nsIPrintSettings>  mPrintSettings;
   nsPrintPreviewListener*     mPPEventListeners;
 
-  char16_t*            mBrandName; //  needed as a substitute name for a document
+  nsString                    mBrandName; //  needed as a substitute name for a document
 
 private:
   nsPrintData() = delete;
diff --git a/layout/printing/nsPrintEngine.cpp b/layout/printing/nsPrintEngine.cpp
index af3288317f69..43a3fb87c38e 100644
--- a/layout/printing/nsPrintEngine.cpp
+++ b/layout/printing/nsPrintEngine.cpp
@@ -1508,7 +1508,7 @@ nsPrintEngine::GetDisplayTitleAndURL(const UniquePtr<nsPrintObject>& aPO,
       if (aDefType == eDocTitleDefURLDoc) {
         if (!aURLStr.IsEmpty()) {
           aTitle = aURLStr;
-        } else if (mPrt->mBrandName) {
+        } else if (!mPrt->mBrandName.IsEmpty()) {
           aTitle = mPrt->mBrandName;
         }
       }
diff --git a/layout/style/ErrorReporter.cpp b/layout/style/ErrorReporter.cpp
index e2cfe3ec7a9a..90156b270b9c 100644
--- a/layout/style/ErrorReporter.cpp
+++ b/layout/style/ErrorReporter.cpp
@@ -315,7 +315,7 @@ ErrorReporter::ReportUnexpected(const char *aMessage)
   if (!ShouldReportErrors()) return;
 
   nsAutoString str;
-  sStringBundle->GetStringFromName(aMessage, getter_Copies(str));
+  sStringBundle->GetStringFromName(aMessage, str);
   AddToError(str);
 }
 
@@ -330,9 +330,8 @@ ErrorReporter::ReportUnexpected(const char *aMessage,
   const char16_t *params[1] = { qparam.get() };
 
   nsAutoString str;
-  sStringBundle->FormatStringFromName(aMessage,
-                                      params, ArrayLength(params),
-                                      getter_Copies(str));
+  sStringBundle->FormatStringFromName(aMessage, params, ArrayLength(params),
+                                      str);
   AddToError(str);
 }
 
@@ -345,9 +344,8 @@ ErrorReporter::ReportUnexpectedUnescaped(const char *aMessage,
   const char16_t *params[1] = { aParam.get() };
 
   nsAutoString str;
-  sStringBundle->FormatStringFromName(aMessage,
-                                      params, ArrayLength(params),
-                                      getter_Copies(str));
+  sStringBundle->FormatStringFromName(aMessage, params, ArrayLength(params),
+                                      str);
   AddToError(str);
 }
 
@@ -375,9 +373,8 @@ ErrorReporter::ReportUnexpected(const char *aMessage,
   const char16_t *params[2] = { tokenString.get(), charStr };
 
   nsAutoString str;
-  sStringBundle->FormatStringFromName(aMessage,
-                                      params, ArrayLength(params),
-                                      getter_Copies(str));
+  sStringBundle->FormatStringFromName(aMessage, params, ArrayLength(params),
+                                      str);
   AddToError(str);
 }
 
@@ -393,9 +390,8 @@ ErrorReporter::ReportUnexpected(const char *aMessage,
   const char16_t *params[2] = { qparam.get(), aValue.get() };
 
   nsAutoString str;
-  sStringBundle->FormatStringFromName(aMessage,
-                                      params, ArrayLength(params),
-                                      getter_Copies(str));
+  sStringBundle->FormatStringFromName(aMessage, params, ArrayLength(params),
+                                      str);
   AddToError(str);
 }
 
@@ -405,13 +401,12 @@ ErrorReporter::ReportUnexpectedEOF(const char *aMessage)
   if (!ShouldReportErrors()) return;
 
   nsAutoString innerStr;
-  sStringBundle->GetStringFromName(aMessage, getter_Copies(innerStr));
+  sStringBundle->GetStringFromName(aMessage, innerStr);
   const char16_t *params[1] = { innerStr.get() };
 
   nsAutoString str;
-  sStringBundle->FormatStringFromName("PEUnexpEOF2",
-                                      params, ArrayLength(params),
-                                      getter_Copies(str));
+  sStringBundle->FormatStringFromName("PEUnexpEOF2", params,
+                                      ArrayLength(params), str);
   AddToError(str);
 }
 
@@ -426,9 +421,8 @@ ErrorReporter::ReportUnexpectedEOF(char16_t aExpected)
   const char16_t *params[1] = { expectedStr };
 
   nsAutoString str;
-  sStringBundle->FormatStringFromName("PEUnexpEOF2",
-                                      params, ArrayLength(params),
-                                      getter_Copies(str));
+  sStringBundle->FormatStringFromName("PEUnexpEOF2", params,
+                                      ArrayLength(params), str);
   AddToError(str);
 }
 
diff --git a/layout/xul/nsMenuFrame.cpp b/layout/xul/nsMenuFrame.cpp
index 36023ec3cae8..d4a26bd5e2db 100644
--- a/layout/xul/nsMenuFrame.cpp
+++ b/layout/xul/nsMenuFrame.cpp
@@ -1102,11 +1102,12 @@ nsMenuFrame::BuildAcceleratorText(bool aNotify)
                                          getter_AddRefs(bundle));
 
         if (NS_SUCCEEDED(rv) && bundle) {
-          nsXPIDLString keyName;
+          nsAutoString keyName;
           rv = bundle->GetStringFromName(NS_ConvertUTF16toUTF8(keyCode).get(),
-                                         getter_Copies(keyName));
-          if (keyName)
+                                         keyName);
+          if (NS_SUCCEEDED(rv)) {
             accelString = keyName;
+          }
         }
       }
 
diff --git a/modules/libpref/nsPrefBranch.cpp b/modules/libpref/nsPrefBranch.cpp
index d862a031ecf1..320713ea99d6 100644
--- a/modules/libpref/nsPrefBranch.cpp
+++ b/modules/libpref/nsPrefBranch.cpp
@@ -325,8 +325,8 @@ NS_IMETHODIMP nsPrefBranch::GetComplexValue(const char *aPrefName, const nsIID &
     // if we need to fetch the default value, do that instead, otherwise use the
     // value we pulled in at the top of this function
     if (bNeedDefault) {
-      nsXPIDLString utf16String;
-      rv = GetDefaultFromPropertiesFile(pref.get(), getter_Copies(utf16String));
+      nsAutoString utf16String;
+      rv = GetDefaultFromPropertiesFile(pref.get(), utf16String);
       if (NS_SUCCEEDED(rv)) {
         theString->SetData(utf16String.get());
       }
@@ -836,7 +836,9 @@ nsPrefBranch::RemoveExpiredCallback(PrefCallback *aCallback)
   mObservers.Remove(aCallback);
 }
 
-nsresult nsPrefBranch::GetDefaultFromPropertiesFile(const char *aPrefName, char16_t **return_buf)
+nsresult
+nsPrefBranch::GetDefaultFromPropertiesFile(const char *aPrefName,
+                                           nsAString& aReturn)
 {
   nsresult rv;
 
@@ -858,7 +860,7 @@ nsresult nsPrefBranch::GetDefaultFromPropertiesFile(const char *aPrefName, char1
   if (NS_FAILED(rv))
     return rv;
 
-  return bundle->GetStringFromName(aPrefName, return_buf);
+  return bundle->GetStringFromName(aPrefName, aReturn);
 }
 
 nsPrefBranch::PrefName
diff --git a/modules/libpref/nsPrefBranch.h b/modules/libpref/nsPrefBranch.h
index 3a086dc773a8..6e0ba6640222 100644
--- a/modules/libpref/nsPrefBranch.h
+++ b/modules/libpref/nsPrefBranch.h
@@ -242,7 +242,7 @@ protected:
 
   virtual ~nsPrefBranch();
 
-  nsresult   GetDefaultFromPropertiesFile(const char *aPrefName, char16_t **return_buf);
+  nsresult   GetDefaultFromPropertiesFile(const char *aPrefName, nsAString& aReturn);
   // As SetCharPref, but without any check on the length of |aValue|
   nsresult   SetCharPrefInternal(const char *aPrefName, const char *aValue);
   // Reject strings that are more than 1Mb, warn if strings are more than 16kb
diff --git a/netwerk/protocol/ftp/nsFtpConnectionThread.cpp b/netwerk/protocol/ftp/nsFtpConnectionThread.cpp
index ea226e334e3e..1091ca308210 100644
--- a/netwerk/protocol/ftp/nsFtpConnectionThread.cpp
+++ b/netwerk/protocol/ftp/nsFtpConnectionThread.cpp
@@ -943,10 +943,10 @@ nsFtpState::R_syst() {
             char16_t* ucs2Response = ToNewUnicode(mResponseMsg);
             const char16_t *formatStrings[1] = { ucs2Response };
 
-            nsXPIDLString formattedString;
+            nsAutoString formattedString;
             rv = bundle->FormatStringFromName("UnsupportedFTPServer",
                                               formatStrings, 1,
-                                              getter_Copies(formattedString));
+                                              formattedString);
             free(ucs2Response);
             if (NS_FAILED(rv))
                 return FTP_ERROR;
diff --git a/netwerk/protocol/gio/nsGIOProtocolHandler.cpp b/netwerk/protocol/gio/nsGIOProtocolHandler.cpp
index b39e126e6761..05830d928694 100644
--- a/netwerk/protocol/gio/nsGIOProtocolHandler.cpp
+++ b/netwerk/protocol/gio/nsGIOProtocolHandler.cpp
@@ -828,17 +828,17 @@ mount_operation_ask_password (GMountOperation   *mount_op,
       if (!realm.IsEmpty()) {
         const char16_t *strings[] = { realm.get(), dispHost.get() };
         bundle->FormatStringFromName("EnterLoginForRealm3",
-                                     strings, 2, getter_Copies(nsmessage));
+                                     strings, 2, nsmessage);
       } else {
         const char16_t *strings[] = { dispHost.get() };
         bundle->FormatStringFromName("EnterUserPasswordFor2",
-                                     strings, 1, getter_Copies(nsmessage));
+                                     strings, 1, nsmessage);
       }
     } else {
       NS_ConvertUTF8toUTF16 userName(default_user);
       const char16_t *strings[] = { userName.get(), dispHost.get() };
       bundle->FormatStringFromName("EnterPasswordFor",
-                                   strings, 2, getter_Copies(nsmessage));
+                                   strings, 2, nsmessage);
     }
   } else {
     g_warning("Unknown mount operation request (flags: %x)", flags);
diff --git a/netwerk/protocol/http/HttpBaseChannel.cpp b/netwerk/protocol/http/HttpBaseChannel.cpp
index f8ab13b5581a..f3aece9d5572 100644
--- a/netwerk/protocol/http/HttpBaseChannel.cpp
+++ b/netwerk/protocol/http/HttpBaseChannel.cpp
@@ -2487,7 +2487,7 @@ HttpBaseChannel::AddSecurityMessage(const nsAString &aMessageTag,
 
   auto innerWindowID = loadInfo->GetInnerWindowID();
 
-  nsXPIDLString errorText;
+  nsAutoString errorText;
   rv = nsContentUtils::GetLocalizedString(
           nsContentUtils::eSECURITY_PROPERTIES,
           NS_ConvertUTF16toUTF8(aMessageTag).get(),
diff --git a/netwerk/protocol/http/nsCORSListenerProxy.cpp b/netwerk/protocol/http/nsCORSListenerProxy.cpp
index 13ea642b6b32..8daa012bef96 100644
--- a/netwerk/protocol/http/nsCORSListenerProxy.cpp
+++ b/netwerk/protocol/http/nsCORSListenerProxy.cpp
@@ -72,7 +72,7 @@ LogBlockedRequest(nsIRequest* aRequest,
   }
 
   // Generate the error message
-  nsXPIDLString blockedMessage;
+  nsAutoString blockedMessage;
   NS_ConvertUTF8toUTF16 specUTF16(spec);
   const char16_t* params[] = { specUTF16.get(), aParam };
   rv = nsContentUtils::FormatLocalizedString(nsContentUtils::eSECURITY_PROPERTIES,
diff --git a/netwerk/protocol/http/nsHttpChannel.cpp b/netwerk/protocol/http/nsHttpChannel.cpp
index 8edcd0848409..8f192e016e76 100644
--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -2809,11 +2809,9 @@ nsHttpChannel::PromptTempRedirect()
     rv = bundleService->CreateBundle(NECKO_MSGS_URL, getter_AddRefs(stringBundle));
     if (NS_FAILED(rv)) return rv;
 
-    nsXPIDLString messageString;
-    rv = stringBundle->GetStringFromName("RepostFormData",
-                                         getter_Copies(messageString));
-    // GetStringFromName can return NS_OK and nullptr messageString.
-    if (NS_SUCCEEDED(rv) && messageString) {
+    nsAutoString messageString;
+    rv = stringBundle->GetStringFromName("RepostFormData", messageString);
+    if (NS_SUCCEEDED(rv)) {
         bool repost = false;
 
         nsCOMPtr<nsIPrompt> prompt;
@@ -2821,7 +2819,7 @@ nsHttpChannel::PromptTempRedirect()
         if (!prompt)
             return NS_ERROR_NO_INTERFACE;
 
-        prompt->Confirm(nullptr, messageString, &repost);
+        prompt->Confirm(nullptr, messageString.get(), &repost);
         if (!repost)
             return NS_ERROR_FAILURE;
     }
diff --git a/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp b/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp
index f64299aa7f70..9f34fc4a29ce 100644
--- a/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp
+++ b/netwerk/protocol/http/nsHttpChannelAuthProvider.cpp
@@ -1586,9 +1586,9 @@ nsHttpChannelAuthProvider::ConfirmAuth(const char* bundleKey,
 
     const char16_t *strs[2] = { ucsHost.get(), ucsUser.get() };
 
-    nsXPIDLString msg;
-    bundle->FormatStringFromName(bundleKey, strs, 2, getter_Copies(msg));
-    if (!msg)
+    nsAutoString msg;
+    rv = bundle->FormatStringFromName(bundleKey, strs, 2, msg);
+    if (NS_FAILED(rv))
         return true;
 
     nsCOMPtr<nsIInterfaceRequestor> callbacks;
@@ -1614,7 +1614,7 @@ nsHttpChannelAuthProvider::ConfirmAuth(const char* bundleKey,
     if (doYesNoPrompt) {
         int32_t choice;
         bool checkState = false;
-        rv = prompt->ConfirmEx(nullptr, msg,
+        rv = prompt->ConfirmEx(nullptr, msg.get(),
                                nsIPrompt::BUTTON_POS_1_DEFAULT +
                                nsIPrompt::STD_YES_NO_BUTTONS,
                                nullptr, nullptr, nullptr, nullptr,
@@ -1625,7 +1625,7 @@ nsHttpChannelAuthProvider::ConfirmAuth(const char* bundleKey,
         confirmed = choice == 0;
     }
     else {
-        rv = prompt->Confirm(nullptr, msg, &confirmed);
+        rv = prompt->Confirm(nullptr, msg.get(), &confirmed);
         if (NS_FAILED(rv))
             return true;
     }
diff --git a/netwerk/streamconv/converters/nsIndexedToHTML.cpp b/netwerk/streamconv/converters/nsIndexedToHTML.cpp
index efd4ca2050ce..af9be9e9e545 100644
--- a/netwerk/streamconv/converters/nsIndexedToHTML.cpp
+++ b/netwerk/streamconv/converters/nsIndexedToHTML.cpp
@@ -515,7 +515,7 @@ nsIndexedToHTML::DoOnStartRequest(nsIRequest* request, nsISupports *aContext,
     htmlEscSpec.Adopt(nsEscapeHTML2(unEscapeSpec.get(),
                                     unEscapeSpec.Length()));
 
-    nsXPIDLString title;
+    nsAutoString title;
     const char16_t* formatTitle[] = {
         htmlEscSpec.get()
     };
@@ -523,7 +523,7 @@ nsIndexedToHTML::DoOnStartRequest(nsIRequest* request, nsISupports *aContext,
     rv = mBundle->FormatStringFromName("DirTitle",
                                        formatTitle,
                                        sizeof(formatTitle)/sizeof(char16_t*),
-                                       getter_Copies(title));
+                                       title);
     if (NS_FAILED(rv)) return rv;
 
     // we want to convert string bundle to NCR
@@ -576,16 +576,15 @@ nsIndexedToHTML::DoOnStartRequest(nsIRequest* request, nsISupports *aContext,
     rv = mBundle->FormatStringFromName("DirTitle",
                                        formatHeading,
                                        sizeof(formatHeading)/sizeof(char16_t*),
-                                       getter_Copies(title));
+                                       title);
     if (NS_FAILED(rv)) return rv;
 
     AppendNonAsciiToNCR(title, buffer);
     buffer.AppendLiteral("</h1>\n");
 
     if (!parentStr.IsEmpty()) {
-        nsXPIDLString parentText;
-        rv = mBundle->GetStringFromName("DirGoUp",
-                                        getter_Copies(parentText));
+        nsAutoString parentText;
+        rv = mBundle->GetStringFromName("DirGoUp", parentText);
         if (NS_FAILED(rv)) return rv;
 
         buffer.AppendLiteral("<p id=\"UI_goUp\"><a class=\"up\" href=\"");
@@ -599,9 +598,8 @@ nsIndexedToHTML::DoOnStartRequest(nsIRequest* request, nsISupports *aContext,
     }
 
     if (isSchemeFile) {
-        nsXPIDLString showHiddenText;
-        rv = mBundle->GetStringFromName("ShowHidden",
-                                        getter_Copies(showHiddenText));
+        nsAutoString showHiddenText;
+        rv = mBundle->GetStringFromName("ShowHidden", showHiddenText);
         if (NS_FAILED(rv)) return rv;
 
         buffer.AppendLiteral("<p id=\"UI_showHidden\" style=\"display:none\"><label><input type=\"checkbox\" checked onchange=\"updateHidden()\">");
@@ -609,30 +607,25 @@ nsIndexedToHTML::DoOnStartRequest(nsIRequest* request, nsISupports *aContext,
         buffer.AppendLiteral("</label></p>\n");
     }
 
-    buffer.AppendLiteral("<table>\n");
-
-    nsXPIDLString columnText;
-
-    buffer.AppendLiteral(" <thead>\n"
+    buffer.AppendLiteral("<table>\n"
+                         " <thead>\n"
                          "  <tr>\n"
                          "   <th>");
 
-    rv = mBundle->GetStringFromName("DirColName",
-                                    getter_Copies(columnText));
+    nsAutoString columnText;
+    rv = mBundle->GetStringFromName("DirColName", columnText);
     if (NS_FAILED(rv)) return rv;
     AppendNonAsciiToNCR(columnText, buffer);
     buffer.AppendLiteral("</th>\n"
                          "   <th>");
 
-    rv = mBundle->GetStringFromName("DirColSize",
-                                    getter_Copies(columnText));
+    rv = mBundle->GetStringFromName("DirColSize", columnText);
     if (NS_FAILED(rv)) return rv;
     AppendNonAsciiToNCR(columnText, buffer);
     buffer.AppendLiteral("</th>\n"
                          "   <th colspan=\"2\">");
 
-    rv = mBundle->GetStringFromName("DirColMTime",
-                                    getter_Copies(columnText));
+    rv = mBundle->GetStringFromName("DirColMTime", columnText);
     if (NS_FAILED(rv)) return rv;
     AppendNonAsciiToNCR(columnText, buffer);
     buffer.AppendLiteral("</th>\n"
@@ -792,9 +785,8 @@ nsIndexedToHTML::OnIndexAvailable(nsIRequest *aRequest,
         }
         pushBuffer.AppendLiteral("?size=16\" alt=\"");
 
-        nsXPIDLString altText;
-        rv = mBundle->GetStringFromName("DirFileLabel",
-                                        getter_Copies(altText));
+        nsAutoString altText;
+        rv = mBundle->GetStringFromName("DirFileLabel", altText);
         if (NS_FAILED(rv)) return rv;
         AppendNonAsciiToNCR(altText, pushBuffer);
         pushBuffer.AppendLiteral("\">");
diff --git a/parser/html/nsHtml5PlainTextUtils.cpp b/parser/html/nsHtml5PlainTextUtils.cpp
index 079543eb3efd..e68522987784 100644
--- a/parser/html/nsHtml5PlainTextUtils.cpp
+++ b/parser/html/nsHtml5PlainTextUtils.cpp
@@ -32,9 +32,9 @@ nsHtml5PlainTextUtils::NewLinkAttributes()
   rv = bundleService->CreateBundle("chrome://global/locale/browser.properties",
                                    getter_AddRefs(bundle));
   NS_ASSERTION(NS_SUCCEEDED(rv) && bundle, "chrome://global/locale/browser.properties could not be loaded");
-  nsXPIDLString title;
+  nsAutoString title;
   if (bundle) {
-    bundle->GetStringFromName("plainText.wordWrap", getter_Copies(title));
+    bundle->GetStringFromName("plainText.wordWrap", title);
   }
 
   linkAttrs->addAttribute(
diff --git a/parser/html/nsHtml5TreeOperation.cpp b/parser/html/nsHtml5TreeOperation.cpp
index 5c507fae1760..eacd3ff7a234 100644
--- a/parser/html/nsHtml5TreeOperation.cpp
+++ b/parser/html/nsHtml5TreeOperation.cpp
@@ -932,7 +932,7 @@ nsHtml5TreeOperation::Perform(nsHtml5TreeOpExecutor* aBuilder,
       }
 
       nsresult rv;
-      nsXPIDLString message;
+      nsAutoString message;
       if (otherAtom) {
         const char16_t* params[] = { atom->GetUTF16String(),
                                       otherAtom->GetUTF16String() };
diff --git a/parser/htmlparser/nsParserMsgUtils.cpp b/parser/htmlparser/nsParserMsgUtils.cpp
index 8d317f97c93e..43d2e64d844e 100644
--- a/parser/htmlparser/nsParserMsgUtils.cpp
+++ b/parser/htmlparser/nsParserMsgUtils.cpp
@@ -35,9 +35,9 @@ nsParserMsgUtils::GetLocalizedStringByName(const char * aPropFileName, const cha
   nsCOMPtr<nsIStringBundle> bundle;
   nsresult rv = GetBundle(aPropFileName,getter_AddRefs(bundle));
   if (NS_SUCCEEDED(rv) && bundle) {
-    nsXPIDLString valUni;
-    rv = bundle->GetStringFromName(aKey, getter_Copies(valUni));
-    if (NS_SUCCEEDED(rv) && valUni) {
+    nsAutoString valUni;
+    rv = bundle->GetStringFromName(aKey, valUni);
+    if (NS_SUCCEEDED(rv)) {
       oVal.Assign(valUni);
     }
   }
@@ -53,11 +53,11 @@ nsParserMsgUtils::GetLocalizedStringByID(const char * aPropFileName, uint32_t aI
   nsCOMPtr<nsIStringBundle> bundle;
   nsresult rv = GetBundle(aPropFileName,getter_AddRefs(bundle));
   if (NS_SUCCEEDED(rv) && bundle) {
-    nsXPIDLString valUni;
-    rv = bundle->GetStringFromID(aID, getter_Copies(valUni));
-    if (NS_SUCCEEDED(rv) && valUni) {
+    nsAutoString valUni;
+    rv = bundle->GetStringFromID(aID, valUni);
+    if (NS_SUCCEEDED(rv)) {
       oVal.Assign(valUni);
-    }  
+    }
   }
 
   return rv;
diff --git a/security/manager/pki/nsNSSDialogs.cpp b/security/manager/pki/nsNSSDialogs.cpp
index 940f5e6f3b20..f5ff94c82fab 100644
--- a/security/manager/pki/nsNSSDialogs.cpp
+++ b/security/manager/pki/nsNSSDialogs.cpp
@@ -320,7 +320,7 @@ nsNSSDialogs::GetPKCS12FilePassword(nsIInterfaceRequestor* ctx,
 
   nsAutoString msg;
   nsresult rv = mPIPStringBundle->GetStringFromName(
-    "getPKCS12FilePasswordMessage", getter_Copies(msg));
+    "getPKCS12FilePasswordMessage", msg);
   if (NS_FAILED(rv)) {
     return rv;
   }
diff --git a/security/manager/ssl/NSSErrorsService.cpp b/security/manager/ssl/NSSErrorsService.cpp
index 5409103d98cb..7736cd8908ae 100644
--- a/security/manager/ssl/NSSErrorsService.cpp
+++ b/security/manager/ssl/NSSErrorsService.cpp
@@ -193,7 +193,7 @@ NSSErrorsService::GetErrorMessage(nsresult aXPCOMErrorCode, nsAString &aErrorMes
   }
 
   nsAutoString msg;
-  nsresult rv = theBundle->GetStringFromName(id_str, getter_Copies(msg));
+  nsresult rv = theBundle->GetStringFromName(id_str, msg);
   if (NS_SUCCEEDED(rv)) {
     aErrorMessage = msg;
   }
diff --git a/security/manager/ssl/nsNSSCertHelper.cpp b/security/manager/ssl/nsNSSCertHelper.cpp
index b7fe41f4144a..2d33eefd3611 100644
--- a/security/manager/ssl/nsNSSCertHelper.cpp
+++ b/security/manager/ssl/nsNSSCertHelper.cpp
@@ -106,8 +106,7 @@ GetPIPNSSBundleString(const char* stringName, nsAString& result)
     return rv;
   }
   result.Truncate();
-  return pipnssBundle->GetStringFromName(stringName,
-                                         getter_Copies(result));
+  return pipnssBundle->GetStringFromName(stringName, result);
 }
 
 static nsresult
@@ -126,7 +125,7 @@ PIPBundleFormatStringFromName(const char* stringName, const char16_t** params,
   }
   result.Truncate();
   return pipnssBundle->FormatStringFromName(
-    stringName, params, numParams, getter_Copies(result));
+    stringName, params, numParams, result);
 }
 
 static nsresult
diff --git a/security/manager/ssl/nsNSSComponent.cpp b/security/manager/ssl/nsNSSComponent.cpp
index 201b78324e78..2698b85b78fd 100644
--- a/security/manager/ssl/nsNSSComponent.cpp
+++ b/security/manager/ssl/nsNSSComponent.cpp
@@ -238,10 +238,8 @@ nsNSSComponent::PIPBundleFormatStringFromName(const char* name,
   nsresult rv = NS_ERROR_FAILURE;
 
   if (mPIPNSSBundle && name) {
-    nsXPIDLString result;
-    rv = mPIPNSSBundle->FormatStringFromName(name,
-                                             params, numParams,
-                                             getter_Copies(result));
+    nsAutoString result;
+    rv = mPIPNSSBundle->FormatStringFromName(name, params, numParams, result);
     if (NS_SUCCEEDED(rv)) {
       outString = result;
     }
@@ -257,8 +255,8 @@ nsNSSComponent::GetPIPNSSBundleString(const char* name, nsAString& outString)
 
   outString.SetLength(0);
   if (mPIPNSSBundle && name) {
-    nsXPIDLString result;
-    rv = mPIPNSSBundle->GetStringFromName(name, getter_Copies(result));
+    nsAutoString result;
+    rv = mPIPNSSBundle->GetStringFromName(name, result);
     if (NS_SUCCEEDED(rv)) {
       outString = result;
       rv = NS_OK;
@@ -276,8 +274,8 @@ nsNSSComponent::GetNSSBundleString(const char* name, nsAString& outString)
 
   outString.SetLength(0);
   if (mNSSErrorsBundle && name) {
-    nsXPIDLString result;
-    rv = mNSSErrorsBundle->GetStringFromName(name, getter_Copies(result));
+    nsAutoString result;
+    rv = mNSSErrorsBundle->GetStringFromName(name, result);
     if (NS_SUCCEEDED(rv)) {
       outString = result;
       rv = NS_OK;
diff --git a/testing/web-platform/meta/dom/historical.html.ini b/testing/web-platform/meta/dom/historical.html.ini
index 5179691ea0b3..c667890b3324 100644
--- a/testing/web-platform/meta/dom/historical.html.ini
+++ b/testing/web-platform/meta/dom/historical.html.ini
@@ -12,10 +12,6 @@
     expected: FAIL
     bug: 660660
 
-  [Node member must be nuked: rootNode]
-    disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1303802
-    bug: 1269155
-
   [Historical DOM features must be removed: async]
     expected: FAIL
 
diff --git a/toolkit/components/downloads/nsDownloadManager.cpp b/toolkit/components/downloads/nsDownloadManager.cpp
index db4eca44d706..fb57e3c71000 100644
--- a/toolkit/components/downloads/nsDownloadManager.cpp
+++ b/toolkit/components/downloads/nsDownloadManager.cpp
@@ -117,8 +117,8 @@ nsDownloadManager::GetDefaultDownloadsDirectory(nsIFile **aResult)
   // Linux:
   // XDG user dir spec, with a fallback to Home/Downloads
 
-  nsXPIDLString folderName;
-  mBundle->GetStringFromName("downloadsFolder", getter_Copies(folderName));
+  nsAutoString folderName;
+  mBundle->GetStringFromName("downloadsFolder", folderName);
 
 #if defined (XP_MACOSX)
   rv = dirService->Get(NS_OSX_DEFAULT_DOWNLOAD_DIR,
diff --git a/toolkit/components/places/Database.cpp b/toolkit/components/places/Database.cpp
index d750dfc2fc9a..4fd79ae0995f 100644
--- a/toolkit/components/places/Database.cpp
+++ b/toolkit/components/places/Database.cpp
@@ -222,7 +222,7 @@ SetJournalMode(nsCOMPtr<mozIStorageConnection>& aDBConn,
 nsresult
 CreateRoot(nsCOMPtr<mozIStorageConnection>& aDBConn,
            const nsCString& aRootName, const nsCString& aGuid,
-           const nsXPIDLString& titleString)
+           const nsAString& titleString)
 {
   MOZ_ASSERT(NS_IsMainThread());
 
@@ -1220,36 +1220,32 @@ Database::CreateBookmarkRoots()
   nsresult rv = bundleService->CreateBundle(PLACES_BUNDLE, getter_AddRefs(bundle));
   if (NS_FAILED(rv)) return rv;
 
-  nsXPIDLString rootTitle;
+  nsAutoString rootTitle;
   // The first root's title is an empty string.
   rv = CreateRoot(mMainConn, NS_LITERAL_CSTRING("places"),
                   NS_LITERAL_CSTRING("root________"), rootTitle);
   if (NS_FAILED(rv)) return rv;
 
   // Fetch the internationalized folder name from the string bundle.
-  rv = bundle->GetStringFromName("BookmarksMenuFolderTitle",
-                                 getter_Copies(rootTitle));
+  rv = bundle->GetStringFromName("BookmarksMenuFolderTitle", rootTitle);
   if (NS_FAILED(rv)) return rv;
   rv = CreateRoot(mMainConn, NS_LITERAL_CSTRING("menu"),
                   NS_LITERAL_CSTRING("menu________"), rootTitle);
   if (NS_FAILED(rv)) return rv;
 
-  rv = bundle->GetStringFromName("BookmarksToolbarFolderTitle",
-                                 getter_Copies(rootTitle));
+  rv = bundle->GetStringFromName("BookmarksToolbarFolderTitle", rootTitle);
   if (NS_FAILED(rv)) return rv;
   rv = CreateRoot(mMainConn, NS_LITERAL_CSTRING("toolbar"),
                   NS_LITERAL_CSTRING("toolbar_____"), rootTitle);
   if (NS_FAILED(rv)) return rv;
 
-  rv = bundle->GetStringFromName("TagsFolderTitle",
-                                 getter_Copies(rootTitle));
+  rv = bundle->GetStringFromName("TagsFolderTitle", rootTitle);
   if (NS_FAILED(rv)) return rv;
   rv = CreateRoot(mMainConn, NS_LITERAL_CSTRING("tags"),
                   NS_LITERAL_CSTRING("tags________"), rootTitle);
   if (NS_FAILED(rv)) return rv;
 
-  rv = bundle->GetStringFromName("OtherBookmarksFolderTitle",
-                                 getter_Copies(rootTitle));
+  rv = bundle->GetStringFromName("OtherBookmarksFolderTitle", rootTitle);
   if (NS_FAILED(rv)) return rv;
   rv = CreateRoot(mMainConn, NS_LITERAL_CSTRING("unfiled"),
                   NS_LITERAL_CSTRING("unfiled_____"), rootTitle);
@@ -1401,9 +1397,8 @@ Database::UpdateBookmarkRootTitles()
                                  };
 
   for (uint32_t i = 0; i < ArrayLength(rootGuids); ++i) {
-    nsXPIDLString title;
-    rv = bundle->GetStringFromName(titleStringIDs[i],
-                                   getter_Copies(title));
+    nsAutoString title;
+    rv = bundle->GetStringFromName(titleStringIDs[i], title);
     if (NS_FAILED(rv)) return rv;
 
     nsCOMPtr<mozIStorageBindingParams> params;
diff --git a/toolkit/components/places/nsNavHistory.cpp b/toolkit/components/places/nsNavHistory.cpp
index 429b07087753..4e52752529fa 100644
--- a/toolkit/components/places/nsNavHistory.cpp
+++ b/toolkit/components/places/nsNavHistory.cpp
@@ -4221,9 +4221,8 @@ nsNavHistory::GetAgeInDaysString(int32_t aInt, const char* aName,
     nsAutoString intString;
     intString.AppendInt(aInt);
     const char16_t* strings[1] = { intString.get() };
-    nsXPIDLString value;
-    nsresult rv = bundle->FormatStringFromName(aName, strings,
-                                               1, getter_Copies(value));
+    nsAutoString value;
+    nsresult rv = bundle->FormatStringFromName(aName, strings, 1, value);
     if (NS_SUCCEEDED(rv)) {
       CopyUTF16toUTF8(value, aResult);
       return;
@@ -4237,8 +4236,8 @@ nsNavHistory::GetStringFromName(const char* aName, nsACString& aResult)
 {
   nsIStringBundle *bundle = GetBundle();
   if (bundle) {
-    nsXPIDLString value;
-    nsresult rv = bundle->GetStringFromName(aName, getter_Copies(value));
+    nsAutoString value;
+    nsresult rv = bundle->GetStringFromName(aName, value);
     if (NS_SUCCEEDED(rv)) {
       CopyUTF16toUTF8(value, aResult);
       return;
diff --git a/toolkit/components/printingui/win/nsPrintDialogUtil.cpp b/toolkit/components/printingui/win/nsPrintDialogUtil.cpp
index 83fcc8f8b968..e4dc40b12af7 100644
--- a/toolkit/components/printingui/win/nsPrintDialogUtil.cpp
+++ b/toolkit/components/printingui/win/nsPrintDialogUtil.cpp
@@ -108,9 +108,9 @@ GetLocalizedString(nsIStringBundle* aStrBundle, const char* aKey, nsString& oVal
   NS_ENSURE_ARG_POINTER(aKey);
 
   // Determine default label from string bundle
-  nsXPIDLString valUni;
-  nsresult rv = aStrBundle->GetStringFromName(aKey, getter_Copies(valUni));
-  if (NS_SUCCEEDED(rv) && valUni) {
+  nsAutoString valUni;
+  nsresult rv = aStrBundle->GetStringFromName(aKey, valUni);
+  if (NS_SUCCEEDED(rv)) {
     oVal.Assign(valUni);
   } else {
     oVal.Truncate();
diff --git a/toolkit/mozapps/extensions/AddonContentPolicy.cpp b/toolkit/mozapps/extensions/AddonContentPolicy.cpp
index 72534fc2a74c..85ba4ba49f73 100644
--- a/toolkit/mozapps/extensions/AddonContentPolicy.cpp
+++ b/toolkit/mozapps/extensions/AddonContentPolicy.cpp
@@ -198,6 +198,7 @@ class CSPValidator final : public nsCSPSrcVisitor {
     {
       // Start with the default error message for a missing directive, since no
       // visitors will be called if the directive isn't present.
+      mError.SetIsVoid(true);
       if (aDirectiveRequired) {
         FormatError("csp.error.missing-directive");
       }
@@ -368,8 +369,8 @@ class CSPValidator final : public nsCSPSrcVisitor {
       nsCOMPtr<nsIStringBundle> stringBundle = GetStringBundle();
 
       if (stringBundle) {
-        rv = stringBundle->FormatStringFromName(aName, aParams, aLength,
-                                                getter_Copies(mError));
+        rv =
+          stringBundle->FormatStringFromName(aName, aParams, aLength, mError);
       }
 
       if (NS_WARN_IF(NS_FAILED(rv))) {
@@ -382,7 +383,7 @@ class CSPValidator final : public nsCSPSrcVisitor {
 
     nsAutoString mURL;
     NS_ConvertASCIItoUTF16 mDirective;
-    nsXPIDLString mError;
+    nsString mError;
 
     bool mFoundSelf;
 };
diff --git a/toolkit/mozapps/extensions/content/extensions.js b/toolkit/mozapps/extensions/content/extensions.js
index 0a9a930806fa..3144daefea39 100644
--- a/toolkit/mozapps/extensions/content/extensions.js
+++ b/toolkit/mozapps/extensions/content/extensions.js
@@ -107,7 +107,7 @@ XPCOMUtils.defineLazyPreferenceGetter(this, "legacyWarningExceptions",
                                       raw => raw.split(","));
 XPCOMUtils.defineLazyPreferenceGetter(this, "legacyExtensionsEnabled",
                                       PREF_LEGACY_ENABLED, true,
-                                      () => gLegacyView.refresh());
+                                      () => gLegacyView.refreshVisibility());
 
 document.addEventListener("load", initialize, true);
 window.addEventListener("unload", shutdown);
@@ -483,7 +483,7 @@ if (window.QueryInterface(Ci.nsIInterfaceRequestor)
 
 var gEventManager = {
   _listeners: {},
-  _installListeners: [],
+  _installListeners: new Set(),
 
   initialize() {
     const ADDON_EVENTS = ["onEnabling", "onEnabled", "onDisabling",
@@ -569,32 +569,22 @@ var gEventManager = {
 
   registerAddonListener(aListener, aAddonId) {
     if (!(aAddonId in this._listeners))
-      this._listeners[aAddonId] = [];
-    else if (this._listeners[aAddonId].indexOf(aListener) != -1)
-      return;
-    this._listeners[aAddonId].push(aListener);
+      this._listeners[aAddonId] = new Set();
+    this._listeners[aAddonId].add(aListener);
   },
 
   unregisterAddonListener(aListener, aAddonId) {
     if (!(aAddonId in this._listeners))
       return;
-    var index = this._listeners[aAddonId].indexOf(aListener);
-    if (index == -1)
-      return;
-    this._listeners[aAddonId].splice(index, 1);
+    this._listeners[aAddonId].delete(aListener);
   },
 
   registerInstallListener(aListener) {
-    if (this._installListeners.indexOf(aListener) != -1)
-      return;
-    this._installListeners.push(aListener);
+    this._installListeners.add(aListener);
   },
 
   unregisterInstallListener(aListener) {
-    var i = this._installListeners.indexOf(aListener);
-    if (i == -1)
-      return;
-    this._installListeners.splice(i, 1);
+    this._installListeners.delete(aListener);
   },
 
   delegateAddonEvent(aEvent, aParams) {
@@ -602,10 +592,9 @@ var gEventManager = {
     if (!(addon.id in this._listeners))
       return;
 
-    var listeners = this._listeners[addon.id];
-    for (let listener of listeners) {
+    function tryListener(listener) {
       if (!(aEvent in listener))
-        continue;
+        return;
       try {
         listener[aEvent].apply(listener, aParams);
       } catch (e) {
@@ -613,6 +602,14 @@ var gEventManager = {
         Cu.reportError(e);
       }
     }
+
+    for (let listener of this._listeners[addon.id]) {
+      tryListener(listener);
+    }
+    // eslint-disable-next-line dot-notation
+    for (let listener of this._listeners["ANY"]) {
+      tryListener(listener);
+    }
   },
 
   delegateInstallEvent(aEvent, aParams) {
@@ -2788,7 +2785,17 @@ var gLegacyView = {
 
     document.getElementById("legacy-learnmore").href = SUPPORT_URL + "webextensions";
 
-    this.refresh();
+    gEventManager.registerAddonListener(this, "ANY");
+
+    this.refreshVisibility();
+  },
+
+  shutdown() {
+    gEventManager.unregisterAddonListener(this, "ANY");
+  },
+
+  onUninstalled() {
+    this.refreshVisibility();
   },
 
   async show(type, request) {
@@ -2824,7 +2831,7 @@ var gLegacyView = {
     return null;
   },
 
-  async refresh() {
+  async refreshVisibility() {
     if (legacyExtensionsEnabled) {
       this._categoryItem.disabled = true;
       return;
@@ -2852,6 +2859,16 @@ var gLegacyView = {
       this._categoryItem.disabled = true;
     }
   },
+
+  getListItemForID(aId) {
+    var listitem = this._listBox.firstChild;
+    while (listitem) {
+      if (listitem.getAttribute("status") == "installed" && listitem.mAddon.id == aId)
+        return listitem;
+      listitem = listitem.nextSibling;
+    }
+    return null;
+  }
 };
 
 var gListView = {
diff --git a/toolkit/mozapps/extensions/test/browser/browser_legacy.js b/toolkit/mozapps/extensions/test/browser/browser_legacy.js
index 575ac93a4069..00a8f04066b1 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_legacy.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_legacy.js
@@ -111,7 +111,7 @@ add_task(async function() {
   // The legacy category does not watch for new installs since new
   // legacy extensions cannot be installed while legacy extensions
   // are disabled, so manually refresh it here.
-  await mgrWin.gLegacyView.refresh();
+  await mgrWin.gLegacyView.refreshVisibility();
 
   // Make sure we re-render the extensions list, after that we should
   // still just have the original two entries.
@@ -156,7 +156,7 @@ add_task(async function() {
   });
 
   // The entry on the left side should now read "Unsupported"
-  await mgrWin.gLegacyView.refresh();
+  await mgrWin.gLegacyView.refreshVisibility();
   is(catItem.disabled, false, "Legacy category is visible");
   is(catItem.getAttribute("name"), get_string("type.unsupported.name"),
      "Category label with unsigned extensions is correct");
@@ -186,7 +186,7 @@ add_task(async function() {
   });
 
   // The name of the pane should go back to "Legacy Extensions"
-  await mgrWin.gLegacyView.refresh();
+  await mgrWin.gLegacyView.refreshVisibility();
   is(catItem.disabled, false, "Legacy category is visible");
   is(catItem.getAttribute("name"), get_string("type.legacy.name"),
      "Category label with no unsigned extensions is correct");
diff --git a/toolkit/system/gnome/nsAlertsIconListener.cpp b/toolkit/system/gnome/nsAlertsIconListener.cpp
index 281cc04591e5..ce00e4eadc01 100644
--- a/toolkit/system/gnome/nsAlertsIconListener.cpp
+++ b/toolkit/system/gnome/nsAlertsIconListener.cpp
@@ -256,8 +256,7 @@ nsAlertsIconListener::InitAlertAsync(nsIAlertNotification* aAlert,
       nsAutoString appName;
 
       if (bundle) {
-        bundle->GetStringFromName("brandShortName",
-                                  getter_Copies(appName));
+        bundle->GetStringFromName("brandShortName", appName);
         appShortName = NS_ConvertUTF16toUTF8(appName);
       } else {
         NS_WARNING("brand.properties not present, using default application name");
diff --git a/toolkit/xre/ProfileReset.cpp b/toolkit/xre/ProfileReset.cpp
index e01d0d99366f..c1ce8e98ceca 100644
--- a/toolkit/xre/ProfileReset.cpp
+++ b/toolkit/xre/ProfileReset.cpp
@@ -87,11 +87,11 @@ ProfileResetCleanup(nsIToolkitProfile* aOldProfile)
   NS_ConvertUTF8toUTF16 appName(gAppData->name);
   const char16_t* params[] = {appName.get(), appName.get()};
 
-  nsXPIDLString resetBackupDirectoryName;
+  nsAutoString resetBackupDirectoryName;
 
   static const char* kResetBackupDirectory = "resetBackupDirectory";
   rv = sb->FormatStringFromName(kResetBackupDirectory, params, 2,
-                                getter_Copies(resetBackupDirectoryName));
+                                resetBackupDirectoryName);
 
   // Get info to copy the old root profile dir to the desktop as a backup.
   nsCOMPtr<nsIFile> backupDest, containerDest, profileDest;
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
index 865e3d9a6caa..b2d1d164f224 100644
--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -1957,23 +1957,21 @@ ProfileLockedDialog(nsIFile* aProfileDir, nsIFile* aProfileLocalDir,
     NS_ConvertUTF8toUTF16 appName(gAppData->name);
     const char16_t* params[] = {appName.get(), appName.get()};
 
-    nsXPIDLString killMessage;
+    nsAutoString killMessage;
 #ifndef XP_MACOSX
-    sb->FormatStringFromName(aUnlocker ? "restartMessageUnlocker"
-                                       : "restartMessageNoUnlocker",
-                             params, 2, getter_Copies(killMessage));
+    rv = sb->FormatStringFromName(aUnlocker ? "restartMessageUnlocker"
+                                            : "restartMessageNoUnlocker",
+                                  params, 2, killMessage);
 #else
-    sb->FormatStringFromName(aUnlocker ? "restartMessageUnlockerMac"
-                                       : "restartMessageNoUnlockerMac",
-                             params, 2, getter_Copies(killMessage));
+    rv = sb->FormatStringFromName(aUnlocker ? "restartMessageUnlockerMac"
+                                            : "restartMessageNoUnlockerMac",
+                                  params, 2, killMessage);
 #endif
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
 
-    nsXPIDLString killTitle;
-    sb->FormatStringFromName("restartTitle",
-                             params, 1, getter_Copies(killTitle));
-
-    if (!killMessage || !killTitle)
-      return NS_ERROR_FAILURE;
+    nsAutoString killTitle;
+    rv = sb->FormatStringFromName("restartTitle", params, 1, killTitle);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_FAILURE);
 
     if (gfxPlatform::IsHeadless()) {
       // TODO: make a way to turn off all dialogs when headless.
@@ -1998,8 +1996,8 @@ ProfileLockedDialog(nsIFile* aProfileDir, nsIFile* aProfileLocalDir,
          nsIPromptService::BUTTON_POS_1);
 
       bool checkState = false;
-      rv = ps->ConfirmEx(nullptr, killTitle, killMessage, flags,
-                         killTitle, nullptr, nullptr, nullptr,
+      rv = ps->ConfirmEx(nullptr, killTitle.get(), killMessage.get(), flags,
+                         killTitle.get(), nullptr, nullptr, nullptr,
                          &checkState, &button);
       NS_ENSURE_SUCCESS_LOG(rv, rv);
 #endif
@@ -2022,7 +2020,7 @@ ProfileLockedDialog(nsIFile* aProfileDir, nsIFile* aProfileLocalDir,
                                   nullptr, aResult);
       }
 #else
-      rv = ps->Alert(nullptr, killTitle, killMessage);
+      rv = ps->Alert(nullptr, killTitle.get(), killMessage.get());
       NS_ENSURE_SUCCESS_LOG(rv, rv);
 #endif
     }
@@ -2055,23 +2053,19 @@ ProfileMissingDialog(nsINativeAppSupport* aNative)
     NS_ConvertUTF8toUTF16 appName(gAppData->name);
     const char16_t* params[] = {appName.get(), appName.get()};
 
-    nsXPIDLString missingMessage;
-
     // profileMissing
-    sb->FormatStringFromName("profileMissing",
-                             params, 2, getter_Copies(missingMessage));
+    nsAutoString missingMessage;
+    rv = sb->FormatStringFromName("profileMissing", params, 2, missingMessage);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_ABORT);
 
-    nsXPIDLString missingTitle;
-    sb->FormatStringFromName("profileMissingTitle",
-                             params, 1, getter_Copies(missingTitle));
+    nsAutoString missingTitle;
+    rv = sb->FormatStringFromName("profileMissingTitle", params, 1, missingTitle);
+    NS_ENSURE_SUCCESS(rv, NS_ERROR_ABORT);
 
-    if (missingMessage && missingTitle) {
-      nsCOMPtr<nsIPromptService> ps
-        (do_GetService(NS_PROMPTSERVICE_CONTRACTID));
-      NS_ENSURE_TRUE(ps, NS_ERROR_FAILURE);
+    nsCOMPtr<nsIPromptService> ps(do_GetService(NS_PROMPTSERVICE_CONTRACTID));
+    NS_ENSURE_TRUE(ps, NS_ERROR_FAILURE);
 
-      ps->Alert(nullptr, missingTitle, missingMessage);
-    }
+    ps->Alert(nullptr, missingTitle.get(), missingMessage.get());
 
     return NS_ERROR_ABORT;
   }
diff --git a/uriloader/base/nsDocLoader.cpp b/uriloader/base/nsDocLoader.cpp
index ac61f5b6bacd..229550088fd1 100644
--- a/uriloader/base/nsDocLoader.cpp
+++ b/uriloader/base/nsDocLoader.cpp
@@ -1162,9 +1162,8 @@ NS_IMETHODIMP nsDocLoader::OnStatus(nsIRequest* aRequest, nsISupports* ctxt,
       mozilla::services::GetStringBundleService();
     if (!sbs)
       return NS_ERROR_FAILURE;
-    nsXPIDLString msg;
-    nsresult rv = sbs->FormatStatusMessage(aStatus, aStatusArg,
-                                           getter_Copies(msg));
+    nsAutoString msg;
+    nsresult rv = sbs->FormatStatusMessage(aStatus, aStatusArg, msg);
     if (NS_FAILED(rv))
       return rv;
 
@@ -1185,7 +1184,7 @@ NS_IMETHODIMP nsDocLoader::OnStatus(nsIRequest* aRequest, nsISupports* ctxt,
       // Put the info at the front of the list
       mStatusInfoList.insertFront(info->mLastStatus);
     }
-    FireOnStatusChange(this, aRequest, aStatus, msg);
+    FireOnStatusChange(this, aRequest, aStatus, msg.get());
   }
   return NS_OK;
 }
diff --git a/uriloader/exthandler/nsExternalHelperAppService.cpp b/uriloader/exthandler/nsExternalHelperAppService.cpp
index d77a0bd56614..749741461724 100644
--- a/uriloader/exthandler/nsExternalHelperAppService.cpp
+++ b/uriloader/exthandler/nsExternalHelperAppService.cpp
@@ -1864,24 +1864,24 @@ void nsExternalAppHandler::SendStatusChange(ErrorType type, nsresult rv, nsIRequ
         nsCOMPtr<nsIStringBundle> bundle;
         if (NS_SUCCEEDED(stringService->CreateBundle("chrome://global/locale/nsWebBrowserPersist.properties",
                          getter_AddRefs(bundle)))) {
-            nsXPIDLString msgText;
+            nsAutoString msgText;
             const char16_t *strings[] = { path.get() };
             if (NS_SUCCEEDED(bundle->FormatStringFromName(msgId, strings, 1,
-                                                          getter_Copies(msgText)))) {
+                                                          msgText))) {
               if (mDialogProgressListener) {
                 // We have a listener, let it handle the error.
-                mDialogProgressListener->OnStatusChange(nullptr, (type == kReadError) ? aRequest : nullptr, rv, msgText);
+                mDialogProgressListener->OnStatusChange(nullptr, (type == kReadError) ? aRequest : nullptr, rv, msgText.get());
               } else if (mTransfer) {
-                mTransfer->OnStatusChange(nullptr, (type == kReadError) ? aRequest : nullptr, rv, msgText);
+                mTransfer->OnStatusChange(nullptr, (type == kReadError) ? aRequest : nullptr, rv, msgText.get());
               } else if (XRE_IsParentProcess()) {
                 // We don't have a listener.  Simply show the alert ourselves.
                 nsresult qiRv;
                 nsCOMPtr<nsIPrompt> prompter(do_GetInterface(GetDialogParent(), &qiRv));
-                nsXPIDLString title;
+                nsAutoString title;
                 bundle->FormatStringFromName("title",
                                              strings,
                                              1,
-                                             getter_Copies(title));
+                                             title);
 
                 MOZ_LOG(nsExternalHelperAppService::mLog, LogLevel::Debug,
                        ("mContentContext=0x%p, prompter=0x%p, qi rv=0x%08"
@@ -1921,7 +1921,7 @@ void nsExternalAppHandler::SendStatusChange(ErrorType type, nsresult rv, nsIRequ
                 }
 
                 // We should always have a prompter at this point.
-                prompter->Alert(title, msgText);
+                prompter->Alert(title.get(), msgText.get());
               }
             }
         }
diff --git a/widget/cocoa/OSXNotificationCenter.mm b/widget/cocoa/OSXNotificationCenter.mm
index cc9007b1565e..4c7849ecfb9d 100644
--- a/widget/cocoa/OSXNotificationCenter.mm
+++ b/widget/cocoa/OSXNotificationCenter.mm
@@ -298,11 +298,11 @@ OSXNotificationCenter::ShowAlertWithIconData(nsIAlertNotification* aAlert,
 
   if (!hostPort.IsEmpty() && bundle) {
     const char16_t* formatStrings[] = { hostPort.get() };
-    nsXPIDLString notificationSource;
+    nsAutoString notificationSource;
     bundle->FormatStringFromName("source.label",
                                  formatStrings,
                                  ArrayLength(formatStrings),
-                                 getter_Copies(notificationSource));
+                                 notificationSource);
     notification.subtitle = nsCocoaUtils::ToNSString(notificationSource);
   }
 
@@ -317,20 +317,17 @@ OSXNotificationCenter::ShowAlertWithIconData(nsIAlertNotification* aAlert,
   // If this is not an application/extension alert, show additional actions dealing with permissions.
   bool isActionable;
   if (bundle && NS_SUCCEEDED(aAlert->GetActionable(&isActionable)) && isActionable) {
-    nsXPIDLString closeButtonTitle, actionButtonTitle, disableButtonTitle, settingsButtonTitle;
-    bundle->GetStringFromName("closeButton.title",
-                              getter_Copies(closeButtonTitle));
-    bundle->GetStringFromName("actionButton.label",
-                              getter_Copies(actionButtonTitle));
+    nsAutoString closeButtonTitle, actionButtonTitle, disableButtonTitle, settingsButtonTitle;
+    bundle->GetStringFromName("closeButton.title", closeButtonTitle);
+    bundle->GetStringFromName("actionButton.label", actionButtonTitle);
     if (!hostPort.IsEmpty()) {
       const char16_t* formatStrings[] = { hostPort.get() };
       bundle->FormatStringFromName("webActions.disableForOrigin.label",
                                    formatStrings,
                                    ArrayLength(formatStrings),
-                                   getter_Copies(disableButtonTitle));
+                                   disableButtonTitle);
     }
-    bundle->GetStringFromName("webActions.settings.label",
-                              getter_Copies(settingsButtonTitle));
+    bundle->GetStringFromName("webActions.settings.label", settingsButtonTitle);
 
     notification.otherButtonTitle = nsCocoaUtils::ToNSString(closeButtonTitle);
 
diff --git a/widget/cocoa/nsFilePicker.mm b/widget/cocoa/nsFilePicker.mm
index 3a783e052ade..eb5c0ab13c4a 100644
--- a/widget/cocoa/nsFilePicker.mm
+++ b/widget/cocoa/nsFilePicker.mm
@@ -119,9 +119,9 @@ NSView* nsFilePicker::GetAccessoryView()
   nsCOMPtr<nsIStringBundle> bundle;
   nsresult rv = sbs->CreateBundle("chrome://global/locale/filepicker.properties", getter_AddRefs(bundle));
   if (NS_SUCCEEDED(rv)) {
-    nsXPIDLString locaLabel;
-    bundle->GetStringFromName("formatLabel", getter_Copies(locaLabel));
-    if (locaLabel) {
+    nsAutoString locaLabel;
+    rv = bundle->GetStringFromName("formatLabel", locaLabel);
+    if (NS_SUCCEEDED(rv)) {
       label = [NSString stringWithCharacters:reinterpret_cast<const unichar*>(locaLabel.get())
                                       length:locaLabel.Length()];
     }
diff --git a/widget/cocoa/nsMenuBarX.mm b/widget/cocoa/nsMenuBarX.mm
index bcd444e7b56c..0ef177f0a326 100644
--- a/widget/cocoa/nsMenuBarX.mm
+++ b/widget/cocoa/nsMenuBarX.mm
@@ -193,14 +193,14 @@ void nsMenuBarX::ConstructFallbackNativeMenus()
     return;
   }
 
-  nsXPIDLString labelUTF16;
-  nsXPIDLString keyUTF16;
+  nsAutoString labelUTF16;
+  nsAutoString keyUTF16;
 
   const char* labelProp = "quitMenuitem.label";
   const char* keyProp = "quitMenuitem.key";
 
-  stringBundle->GetStringFromName(labelProp, getter_Copies(labelUTF16));
-  stringBundle->GetStringFromName(keyProp, getter_Copies(keyUTF16));
+  stringBundle->GetStringFromName(labelProp, labelUTF16);
+  stringBundle->GetStringFromName(keyProp, keyUTF16);
 
   NSString* labelStr = [NSString stringWithUTF8String:
                         NS_ConvertUTF16toUTF8(labelUTF16).get()];
diff --git a/widget/cocoa/nsPrintDialogX.mm b/widget/cocoa/nsPrintDialogX.mm
index 18b96f30fa7b..793239271f47 100644
--- a/widget/cocoa/nsPrintDialogX.mm
+++ b/widget/cocoa/nsPrintDialogX.mm
@@ -307,8 +307,8 @@ static const char sHeaderFooterTags[][4] =  {"", "&T", "&U", "&D", "&P", "&PT"};
   if (!mPrintBundle)
     return @"";
 
-  nsXPIDLString intlString;
-  mPrintBundle->GetStringFromName(aKey, getter_Copies(intlString));
+  nsAutoString intlString;
+  mPrintBundle->GetStringFromName(aKey, intlString);
   NSMutableString* s = [NSMutableString stringWithUTF8String:NS_ConvertUTF16toUTF8(intlString).get()];
 
   // Remove all underscores (they're used in the GTK dialog for accesskeys).
diff --git a/widget/gtk/nsPrintDialogGTK.cpp b/widget/gtk/nsPrintDialogGTK.cpp
index 81ba2f71f18c..9c1f0dbb67ca 100644
--- a/widget/gtk/nsPrintDialogGTK.cpp
+++ b/widget/gtk/nsPrintDialogGTK.cpp
@@ -53,9 +53,9 @@ ShowCustomDialog(GtkComboBox *changed_box, gpointer user_data)
 
   nsCOMPtr<nsIStringBundle> printBundle;
   bundleSvc->CreateBundle("chrome://global/locale/printdialog.properties", getter_AddRefs(printBundle));
-  nsXPIDLString intlString;
+  nsAutoString intlString;
 
-  printBundle->GetStringFromName("headerFooterCustom", getter_Copies(intlString));
+  printBundle->GetStringFromName("headerFooterCustom", intlString);
   GtkWidget* prompt_dialog = gtk_dialog_new_with_buttons(NS_ConvertUTF16toUTF8(intlString).get(), printDialog,
 #if (MOZ_WIDGET_GTK == 2)
                                                          (GtkDialogFlags)(GTK_DIALOG_MODAL | GTK_DIALOG_NO_SEPARATOR),
@@ -71,7 +71,7 @@ ShowCustomDialog(GtkComboBox *changed_box, gpointer user_data)
                                           GTK_RESPONSE_REJECT,
                                           -1);
 
-  printBundle->GetStringFromName("customHeaderFooterPrompt", getter_Copies(intlString));
+  printBundle->GetStringFromName("customHeaderFooterPrompt", intlString);
   GtkWidget* custom_label = gtk_label_new(NS_ConvertUTF16toUTF8(intlString).get());
   GtkWidget* custom_entry = gtk_entry_new();
   GtkWidget* question_icon = gtk_image_new_from_stock(GTK_STOCK_DIALOG_QUESTION, GTK_ICON_SIZE_DIALOG);
@@ -327,8 +327,8 @@ nsPrintDialogWidgetGTK::nsPrintDialogWidgetGTK(nsPIDOMWindowOuter *aParent,
 NS_ConvertUTF16toUTF8
 nsPrintDialogWidgetGTK::GetUTF8FromBundle(const char *aKey)
 {
-  nsXPIDLString intlString;
-  printBundle->GetStringFromName(aKey, getter_Copies(intlString));
+  nsAutoString intlString;
+  printBundle->GetStringFromName(aKey, intlString);
   return NS_ConvertUTF16toUTF8(intlString);  // Return the actual object so we don't lose reference
 }
 
diff --git a/widget/gtk/nsSound.cpp b/widget/gtk/nsSound.cpp
index 7153896ee7fc..c70921c1c801 100644
--- a/widget/gtk/nsSound.cpp
+++ b/widget/gtk/nsSound.cpp
@@ -133,8 +133,7 @@ ca_context_get_default()
                                     getter_AddRefs(brandingBundle));
         if (brandingBundle) {
             nsAutoString wbrand;
-            brandingBundle->GetStringFromName("brandShortName",
-                                              getter_Copies(wbrand));
+            brandingBundle->GetStringFromName("brandShortName", wbrand);
             NS_ConvertUTF16toUTF8 brand(wbrand);
 
             ca_context_change_props(ctx, "application.name", brand.get(),
diff --git a/widget/gtk/nsWindow.cpp b/widget/gtk/nsWindow.cpp
index a623c3ce98eb..c5085dfb61c6 100644
--- a/widget/gtk/nsWindow.cpp
+++ b/widget/gtk/nsWindow.cpp
@@ -175,7 +175,7 @@ static GdkWindow *get_inner_gdk_window (GdkWindow *aWindow,
 static int    is_parent_ungrab_enter(GdkEventCrossing *aEvent);
 static int    is_parent_grab_leave(GdkEventCrossing *aEvent);
 
-static void GetBrandName(nsXPIDLString& brandName);
+static void GetBrandName(nsAString& brandName);
 
 /* callbacks from widgets */
 #if (MOZ_WIDGET_GTK == 2)
@@ -1764,7 +1764,7 @@ nsWindow::SetIcon(const nsAString& aIconSpec)
     nsAutoCString iconName;
 
     if (aIconSpec.EqualsLiteral("default")) {
-        nsXPIDLString brandName;
+        nsAutoString brandName;
         GetBrandName(brandName);
         AppendUTF16toUTF8(brandName, iconName);
         ToLowerCase(iconName);
@@ -3496,7 +3496,7 @@ nsWindow::OnTouchEvent(GdkEventTouch* aEvent)
 #endif
 
 static void
-GetBrandName(nsXPIDLString& brandName)
+GetBrandName(nsAString& aBrandName)
 {
     nsCOMPtr<nsIStringBundleService> bundleService =
         do_GetService(NS_STRINGBUNDLE_CONTRACTID);
@@ -3508,12 +3508,10 @@ GetBrandName(nsXPIDLString& brandName)
             getter_AddRefs(bundle));
 
     if (bundle)
-        bundle->GetStringFromName(
-            "brandShortName",
-            getter_Copies(brandName));
+        bundle->GetStringFromName("brandShortName", aBrandName);
 
-    if (brandName.IsEmpty())
-        brandName.AssignLiteral(u"Mozilla");
+    if (aBrandName.IsEmpty())
+        aBrandName.AssignLiteral(u"Mozilla");
 }
 
 static GdkWindow *
diff --git a/widget/nsBaseFilePicker.cpp b/widget/nsBaseFilePicker.cpp
index 8038ce8b6c38..8259bfe54ee7 100644
--- a/widget/nsBaseFilePicker.cpp
+++ b/widget/nsBaseFilePicker.cpp
@@ -211,51 +211,51 @@ nsBaseFilePicker::AppendFilters(int32_t aFilterMask)
   if (NS_FAILED(rv))
     return NS_ERROR_FAILURE;
 
-  nsXPIDLString title;
-  nsXPIDLString filter;
+  nsAutoString title;
+  nsAutoString filter;
 
   if (aFilterMask & filterAll) {
-    titleBundle->GetStringFromName("allTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("allFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("allTitle", title);
+    filterBundle->GetStringFromName("allFilter", filter);
     AppendFilter(title,filter);
   }
   if (aFilterMask & filterHTML) {
-    titleBundle->GetStringFromName("htmlTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("htmlFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("htmlTitle", title);
+    filterBundle->GetStringFromName("htmlFilter", filter);
     AppendFilter(title,filter);
   }
   if (aFilterMask & filterText) {
-    titleBundle->GetStringFromName("textTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("textFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("textTitle", title);
+    filterBundle->GetStringFromName("textFilter", filter);
     AppendFilter(title,filter);
   }
   if (aFilterMask & filterImages) {
-    titleBundle->GetStringFromName("imageTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("imageFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("imageTitle", title);
+    filterBundle->GetStringFromName("imageFilter", filter);
     AppendFilter(title,filter);
   }
   if (aFilterMask & filterAudio) {
-    titleBundle->GetStringFromName("audioTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("audioFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("audioTitle", title);
+    filterBundle->GetStringFromName("audioFilter", filter);
     AppendFilter(title,filter);
   }
   if (aFilterMask & filterVideo) {
-    titleBundle->GetStringFromName("videoTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("videoFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("videoTitle", title);
+    filterBundle->GetStringFromName("videoFilter", filter);
     AppendFilter(title,filter);
   }
   if (aFilterMask & filterXML) {
-    titleBundle->GetStringFromName("xmlTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("xmlFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("xmlTitle", title);
+    filterBundle->GetStringFromName("xmlFilter", filter);
     AppendFilter(title,filter);
   }
   if (aFilterMask & filterXUL) {
-    titleBundle->GetStringFromName("xulTitle", getter_Copies(title));
-    filterBundle->GetStringFromName("xulFilter", getter_Copies(filter));
+    titleBundle->GetStringFromName("xulTitle", title);
+    filterBundle->GetStringFromName("xulFilter", filter);
     AppendFilter(title, filter);
   }
   if (aFilterMask & filterApps) {
-    titleBundle->GetStringFromName("appsTitle", getter_Copies(title));
+    titleBundle->GetStringFromName("appsTitle", title);
     // Pass the magic string "..apps" to the platform filepicker, which it
     // should recognize and do the correct platform behavior for.
     AppendFilter(title, NS_LITERAL_STRING("..apps"));
diff --git a/widget/windows/AudioSession.cpp b/widget/windows/AudioSession.cpp
index 0e818fd1e114..401278a1b770 100644
--- a/widget/windows/AudioSession.cpp
+++ b/widget/windows/AudioSession.cpp
@@ -209,8 +209,7 @@ AudioSession::Start()
                                 getter_AddRefs(bundle));
     NS_ENSURE_TRUE(bundle, NS_ERROR_FAILURE);
 
-    bundle->GetStringFromName("brandFullName",
-                              getter_Copies(mDisplayName));
+    bundle->GetStringFromName("brandFullName", mDisplayName);
 
     wchar_t *buffer;
     mIconPath.GetMutableData(&buffer, MAX_PATH);
diff --git a/widget/windows/nsDataObj.cpp b/widget/windows/nsDataObj.cpp
index 3dc486cf2b32..962d5ca161ed 100644
--- a/widget/windows/nsDataObj.cpp
+++ b/widget/windows/nsDataObj.cpp
@@ -1079,7 +1079,7 @@ CreateFilenameFromTextW(nsString & aText, const wchar_t * aExtension,
 #define PAGEINFO_PROPERTIES "chrome://navigator/locale/pageInfo.properties"
 
 static bool
-GetLocalizedString(const char* aName, nsXPIDLString & aString)
+GetLocalizedString(const char* aName, nsAString& aString)
 {
   nsCOMPtr<nsIStringBundleService> stringService =
     mozilla::services::GetStringBundleService();
@@ -1092,7 +1092,7 @@ GetLocalizedString(const char* aName, nsXPIDLString & aString)
   if (NS_FAILED(rv))
     return false;
 
-  rv = stringBundle->GetStringFromName(aName, getter_Copies(aString));
+  rv = stringBundle->GetStringFromName(aName, aString);
   return NS_SUCCEEDED(rv);
 }
 
@@ -1124,7 +1124,7 @@ nsDataObj :: GetFileDescriptorInternetShortcutA ( FORMATETC& aFE, STGMEDIUM& aST
   // 2) localized string for an untitled page, 3) just use "Untitled.URL"
   if (!CreateFilenameFromTextA(title, ".URL", 
                                fileGroupDescA->fgd[0].cFileName, NS_MAX_FILEDESCRIPTOR)) {
-    nsXPIDLString untitled;
+    nsAutoString untitled;
     if (!GetLocalizedString("noPageTitle", untitled) ||
         !CreateFilenameFromTextA(untitled, ".URL", 
                                  fileGroupDescA->fgd[0].cFileName, NS_MAX_FILEDESCRIPTOR)) {
@@ -1165,7 +1165,7 @@ nsDataObj :: GetFileDescriptorInternetShortcutW ( FORMATETC& aFE, STGMEDIUM& aST
   // 2) localized string for an untitled page, 3) just use "Untitled.URL"
   if (!CreateFilenameFromTextW(title, L".URL",
                                fileGroupDescW->fgd[0].cFileName, NS_MAX_FILEDESCRIPTOR)) {
-    nsXPIDLString untitled;
+    nsAutoString untitled;
     if (!GetLocalizedString("noPageTitle", untitled) ||
         !CreateFilenameFromTextW(untitled, L".URL",
                                  fileGroupDescW->fgd[0].cFileName, NS_MAX_FILEDESCRIPTOR)) {