Bug 948238 - Read browser.tabs.remote once at startup and never again (r=bsmedberg)

accessible/src/windows/msaa/nsWinUtils.cpp

@@ -58,7 +58,7 @@ nsWinUtils::MaybeStartWindowEmulation()
   // with tabs.
   if (Compatibility::IsJAWS() || Compatibility::IsWE() ||
       Compatibility::IsDolphin() ||
-      Preferences::GetBool("browser.tabs.remote")) {
+      BrowserTabsRemote()) {
     RegisterNativeWindow(kClassNameTabContent);
     sHWNDCache = new nsRefPtrHashtable<nsPtrHashKey<void>, DocAccessible>(4);
     return true;

browser/base/content/browser.js

@@ -742,7 +742,7 @@ var gBrowserInit = {
   delayedStartupFinished: false,
 
   onLoad: function() {
-    gMultiProcessBrowser = gPrefService.getBoolPref("browser.tabs.remote");
+    gMultiProcessBrowser = Services.appinfo.browserTabsRemote;
 
     var mustLoadSidebar = false;
 

browser/base/content/tabbrowser.xml

@@ -3037,7 +3037,7 @@
               "-moz-default-background-color" :
               Services.prefs.getCharPref("browser.display.background_color");
 
-          if (Services.prefs.getBoolPref("browser.tabs.remote")) {
+          if (Services.appinfo.browserTabsRemote) {
             messageManager.addMessageListener("DOMTitleChanged", this);
             messageManager.addMessageListener("contextmenu", this);
           }
@@ -3103,7 +3103,7 @@
           document.removeEventListener("keypress", this, false);
           window.removeEventListener("sizemodechange", this, false);
 
-          if (Services.prefs.getBoolPref("browser.tabs.remote")) {
+          if (Services.appinfo.browserTabsRemote) {
             messageManager.removeMessageListener("DOMTitleChanged", this);
             messageManager.removeMessageListener("contextmenu", this);
           }

browser/components/nsBrowserGlue.js

@@ -481,7 +481,7 @@ BrowserGlue.prototype = {
     SessionStore.init();
     BrowserUITelemetry.init();
 
-    if (Services.prefs.getBoolPref("browser.tabs.remote"))
+    if (Services.appinfo.browserTabsRemote)
       ContentClick.init();
 
     Services.obs.notifyObservers(null, "browser-ui-startup-complete", "");

browser/components/sessionstore/src/SessionStore.jsm

@@ -389,7 +389,7 @@ let SessionStoreInternal = {
       throw new Error("SessionStore.init() must only be called once!");
     }
 
-    this._disabledForMultiProcess = Services.prefs.getBoolPref("browser.tabs.remote");
+    this._disabledForMultiProcess = Services.appinfo.browserTabsRemote;
     if (this._disabledForMultiProcess) {
       this._deferredInitialized.resolve();
       return;

browser/metro/base/content/browser.js

@@ -1429,7 +1429,7 @@ Tab.prototype = {
 
     browser.setAttribute("type", "content");
 
-    let useRemote = Services.prefs.getBoolPref("browser.tabs.remote");
+    let useRemote = Services.appinfo.browserTabsRemote;
     let useLocal = Util.isLocalScheme(aURI);
     browser.setAttribute("remote", (!useLocal && useRemote) ? "true" : "false");
 

dom/ipc/ContentParent.cpp

@@ -79,6 +79,7 @@
 #include "nsISupportsPrimitives.h"
 #include "nsIURIFixup.h"
 #include "nsIWindowWatcher.h"
+#include "nsIXULRuntime.h"
 #include "nsMemoryReporterManager.h"
 #include "nsServiceManagerUtils.h"
 #include "nsStyleSheetService.h"
@@ -3113,7 +3114,7 @@ ContentParent::ShouldContinueFromReplyTimeout()
 {
   // The only time ContentParent sends blocking messages is for CPOWs, so
   // timeouts should only ever occur in electrolysis-enabled sessions.
-  MOZ_ASSERT(Preferences::GetBool("browser.tabs.remote", false));
+  MOZ_ASSERT(BrowserTabsRemote());
   return false;
 }
 

dom/ipc/TabChild.cpp

@@ -55,6 +55,7 @@
 #include "nsIWebBrowserFocus.h"
 #include "nsIWebBrowserSetup.h"
 #include "nsIWebProgress.h"
+#include "nsIXULRuntime.h"
 #include "nsInterfaceHashtable.h"
 #include "nsPIDOMWindow.h"
 #include "nsPIWindowRoot.h"
@@ -2314,8 +2315,8 @@ TabChild::InitRenderingState()
                                      false);
     }
 
-    // This state can't really change during the lifetime of the child.
-    sCpowsEnabled = Preferences::GetBool("browser.tabs.remote", false);
+    // This state can't change during the lifetime of the child.
+    sCpowsEnabled = BrowserTabsRemote();
     if (Preferences::GetBool("dom.ipc.cpows.force-enabled", false))
       sCpowsEnabled = true;
 

gfx/thebes/gfxPlatform.cpp

@@ -85,6 +85,7 @@
 #include "mozilla/Mutex.h"
 
 #include "nsIGfxInfo.h"
+#include "nsIXULRuntime.h"
 
 using namespace mozilla;
 using namespace mozilla::layers;
@@ -2075,7 +2076,7 @@ InitLayersAccelerationPrefs()
     sPrefLayoutFrameRate = Preferences::GetInt("layout.frame_rate", -1);
     sBufferRotationEnabled = Preferences::GetBool("layers.bufferrotation.enabled", true);
     sComponentAlphaEnabled = Preferences::GetBool("layers.componentalpha.enabled", true);
-    sPrefBrowserTabsRemote = Preferences::GetBool("browser.tabs.remote", false);
+    sPrefBrowserTabsRemote = BrowserTabsRemote();
 
 #ifdef XP_WIN
     if (sPrefLayersAccelerationForceEnabled) {

layout/forms/nsListControlFrame.cpp

@@ -16,6 +16,7 @@
 #include "nsIPresShell.h"
 #include "nsEventStateManager.h"
 #include "nsIDOMMouseEvent.h"
+#include "nsIXULRuntime.h"
 #include "nsFontMetrics.h"
 #include "nsIScrollableFrame.h"
 #include "nsCSSRendering.h"
@@ -1806,8 +1807,7 @@ nsListControlFrame::MouseDown(nsIDOMEvent* aMouseEvent)
   } else {
     // NOTE: the combo box is responsible for dropping it down
     if (mComboboxFrame) {
-      if (XRE_GetProcessType() == GeckoProcessType_Content &&
-          Preferences::GetBool("browser.tabs.remote", false)) {
+      if (XRE_GetProcessType() == GeckoProcessType_Content && BrowserTabsRemote()) {
         nsContentUtils::DispatchChromeEvent(mContent->OwnerDoc(), mContent,
                                             NS_LITERAL_STRING("mozshowdropdown"), true,
                                             false);

toolkit/components/satchel/nsFormAutoComplete.js

@@ -488,9 +488,8 @@ FormAutoCompleteResult.prototype = {
 };
 
 
-if (Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT &&
-    Services.prefs.prefHasUserValue("browser.tabs.remote") &&
-    Services.prefs.getBoolPref("browser.tabs.remote")) {
+let remote = Services.appinfo.browserTabsRemote;
+if (Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT && remote) {
   // Register the stub FormAutoComplete module in the child which will
   // forward messages to the parent through the process message manager.
   let component = [FormAutoCompleteChild];

toolkit/xre/nsAppRunner.cpp

@@ -789,6 +789,16 @@ nsXULAppInfo::GetProcessType(uint32_t* aResult)
   return NS_OK;
 }
 
+static bool gBrowserTabsRemote = false;
+static bool gBrowserTabsRemoteInitialized = false;
+
+NS_IMETHODIMP
+nsXULAppInfo::GetBrowserTabsRemote(bool* aResult)
+{
+  *aResult = BrowserTabsRemote();
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsXULAppInfo::EnsureContentProcess()
 {
@@ -4368,6 +4378,17 @@ XRE_GetProcessType()
   return mozilla::startup::sChildProcessType;
 }
 
+bool
+mozilla::BrowserTabsRemote()
+{
+  if (!gBrowserTabsRemoteInitialized) {
+    gBrowserTabsRemote = Preferences::GetBool("browser.tabs.remote", false);
+    gBrowserTabsRemoteInitialized = true;
+  }
+
+  return gBrowserTabsRemote;
+}
+
 void
 SetupErrorHandling(const char* progname)
 {

widget/xpwidgets/nsBaseWidget.cpp

@@ -935,7 +935,7 @@ CheckForBasicBackends(nsTArray<LayersBackend>& aHints)
   for (size_t i = 0; i < aHints.Length(); ++i) {
     if (aHints[i] == LAYERS_BASIC &&
         !Preferences::GetBool("layers.offmainthreadcomposition.force-basic", false) &&
-        !Preferences::GetBool("browser.tabs.remote", false)) {
+        !BrowserTabsRemote()) {
       // basic compositor is not stable enough for regular use
       aHints[i] = LAYERS_NONE;
     }

xpcom/system/nsIXULRuntime.idl

@@ -4,6 +4,15 @@
 
 #include "nsISupports.idl"
 
+%{C++
+
+namespace mozilla {
+// Simple C++ getter for nsIXULRuntime::browserTabsRemote
+bool BrowserTabsRemote();
+}
+
+%}
+
 /**
  * Provides information about the XUL runtime.
  * @status UNSTABLE - This interface is not frozen and will probably change in
@@ -11,7 +20,7 @@
  *                    stable/frozen, please contact Benjamin Smedberg.
  */
 
-[scriptable, uuid(cb0b8eda-4c83-4d0e-a63c-d3b65714bc85)]
+[scriptable, uuid(33bd1630-611e-11e3-949a-0800200c9a66)]
 interface nsIXULRuntime : nsISupports
 {
   /**
@@ -67,6 +76,12 @@ interface nsIXULRuntime : nsISupports
    */
   readonly attribute unsigned long processType;
 
+  /**
+   * If true, browser tabs may be opened in a different process from the main
+   * browser UI.
+   */
+  readonly attribute boolean browserTabsRemote;
+
   /**
    * Signal the apprunner to invalidate caches on the next restart.
    * This will cause components to be autoregistered and all