diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index c868ad04b74f..7bd456fd2f70 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -11295,8 +11295,8 @@ bool nsContentUtils::IsURIInList(nsIURI* aURI, const nsCString& aList) {
 }
 
 /* static */
-ScreenIntMargin nsContentUtils::GetWindowSafeAreaInsets(
-    nsIScreen* aScreen, const ScreenIntMargin& aSafeAreaInsets,
+LayoutDeviceIntMargin nsContentUtils::GetWindowSafeAreaInsets(
+    nsIScreen* aScreen, const LayoutDeviceIntMargin& aSafeAreaInsets,
     const LayoutDeviceIntRect& aWindowRect) {
   // This calculates safe area insets of window from screen rectangle, window
   // rectangle and safe area insets of screen.
@@ -11312,36 +11312,23 @@ ScreenIntMargin nsContentUtils::GetWindowSafeAreaInsets(
   // |  +-------------------------------+     |
   // +----------------------------------------+
   //
-  ScreenIntMargin windowSafeAreaInsets;
-
+  LayoutDeviceIntMargin windowSafeAreaInsets;
   if (windowSafeAreaInsets == aSafeAreaInsets) {
     // no safe area insets.
     return windowSafeAreaInsets;
   }
 
-  int32_t screenLeft, screenTop, screenWidth, screenHeight;
-  nsresult rv =
-      aScreen->GetRect(&screenLeft, &screenTop, &screenWidth, &screenHeight);
-  if (NS_WARN_IF(NS_FAILED(rv))) {
-    return windowSafeAreaInsets;
-  }
-
-  const ScreenIntRect screenRect(screenLeft, screenTop, screenWidth,
-                                 screenHeight);
-
-  ScreenIntRect safeAreaRect = screenRect;
+  const LayoutDeviceIntRect screenRect = aScreen->GetRect();
+  LayoutDeviceIntRect safeAreaRect = screenRect;
   safeAreaRect.Deflate(aSafeAreaInsets);
 
-  ScreenIntRect windowRect = ViewAs<ScreenPixel>(
-      aWindowRect, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
-
   // FIXME(bug 1754323): This can trigger because the screen rect is not
   // orientation-aware.
   // MOZ_ASSERT(screenRect.Contains(windowRect),
   //            "Screen doesn't contain window rect? Something seems off");
 
   // window's rect of safe area
-  safeAreaRect = safeAreaRect.Intersect(windowRect);
+  safeAreaRect = safeAreaRect.Intersect(aWindowRect);
 
   windowSafeAreaInsets.top = safeAreaRect.y - aWindowRect.y;
   windowSafeAreaInsets.left = safeAreaRect.x - aWindowRect.x;
@@ -11350,7 +11337,7 @@ ScreenIntMargin nsContentUtils::GetWindowSafeAreaInsets(
   windowSafeAreaInsets.bottom = aWindowRect.y + aWindowRect.height -
                                 (safeAreaRect.y + safeAreaRect.height);
 
-  windowSafeAreaInsets.EnsureAtLeast(ScreenIntMargin());
+  windowSafeAreaInsets.EnsureAtLeast(LayoutDeviceIntMargin());
   // This shouldn't be needed, but it wallpapers orientation issues, see bug
   // 1754323.
   windowSafeAreaInsets.EnsureAtMost(aSafeAreaInsets);
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index f52475f524a5..f7a858d5349c 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -3423,8 +3423,8 @@ class nsContentUtils {
    * Return safe area insets of window that defines as
    * https://drafts.csswg.org/css-env-1/#safe-area-insets.
    */
-  static mozilla::ScreenIntMargin GetWindowSafeAreaInsets(
-      nsIScreen* aScreen, const mozilla::ScreenIntMargin& aSafeareaInsets,
+  static mozilla::LayoutDeviceIntMargin GetWindowSafeAreaInsets(
+      nsIScreen* aScreen, const mozilla::LayoutDeviceIntMargin& aSafeareaInsets,
       const mozilla::LayoutDeviceIntRect& aWindowRect);
 
   struct SubresourceCacheValidationInfo {
diff --git a/dom/base/nsFrameLoader.cpp b/dom/base/nsFrameLoader.cpp
index d86d469134d7..c333b1dce957 100644
--- a/dom/base/nsFrameLoader.cpp
+++ b/dom/base/nsFrameLoader.cpp
@@ -956,7 +956,7 @@ bool nsFrameLoader::Show(nsSubDocumentFrame* aFrame) {
   if (IsRemoteFrame()) {
     return ShowRemoteFrame(aFrame);
   }
-  const ScreenIntSize size = aFrame->GetSubdocumentSize();
+  const LayoutDeviceIntSize size = aFrame->GetSubdocumentSize();
   nsresult rv = MaybeCreateDocShell();
   if (NS_FAILED(rv)) {
     return false;
@@ -1123,7 +1123,8 @@ bool nsFrameLoader::ShowRemoteFrame(nsSubDocumentFrame* aFrame) {
     baseWindow->GetMainWidget(getter_AddRefs(mainWidget));
     nsSizeMode sizeMode =
         mainWidget ? mainWidget->SizeMode() : nsSizeMode_Normal;
-    const auto size = hasSize ? aFrame->GetSubdocumentSize() : ScreenIntSize();
+    const auto size =
+        hasSize ? aFrame->GetSubdocumentSize() : LayoutDeviceIntSize();
     OwnerShowInfo info(size, GetScrollbarPreference(mOwnerContent), sizeMode);
     if (!mRemoteBrowser->Show(info)) {
       return false;
@@ -2364,7 +2365,7 @@ nsresult nsFrameLoader::CheckForRecursiveLoad(nsIURI* aURI) {
   return NS_OK;
 }
 
-nsresult nsFrameLoader::GetWindowDimensions(nsIntRect& aRect) {
+nsresult nsFrameLoader::GetWindowDimensions(LayoutDeviceIntRect& aRect) {
   if (!mOwnerContent) {
     return NS_ERROR_FAILURE;
   }
@@ -2394,8 +2395,8 @@ nsresult nsFrameLoader::GetWindowDimensions(nsIntRect& aRect) {
   }
 
   nsCOMPtr<nsIBaseWindow> treeOwnerAsWin(do_GetInterface(parentOwner));
-  treeOwnerAsWin->GetPosition(&aRect.x, &aRect.y);
-  treeOwnerAsWin->GetSize(&aRect.width, &aRect.height);
+  aRect.MoveTo(treeOwnerAsWin->GetPosition());
+  aRect.SizeTo(treeOwnerAsWin->GetSize());
   return NS_OK;
 }
 
@@ -2410,8 +2411,8 @@ nsresult nsFrameLoader::UpdatePositionAndSize(nsSubDocumentFrame* aFrame) {
       if (!mRemoteBrowserShown) {
         ShowRemoteFrame(aFrame);
       }
-      nsIntRect dimensions;
-      NS_ENSURE_SUCCESS(GetWindowDimensions(dimensions), NS_ERROR_FAILURE);
+      LayoutDeviceIntRect dimensions;
+      MOZ_TRY(GetWindowDimensions(dimensions));
       mRemoteBrowser->UpdateDimensions(dimensions, size);
       mRemoteBrowserSized = true;
     }
diff --git a/dom/base/nsFrameLoader.h b/dom/base/nsFrameLoader.h
index dfaca9eaaa6d..fe0d16be377e 100644
--- a/dom/base/nsFrameLoader.h
+++ b/dom/base/nsFrameLoader.h
@@ -390,7 +390,7 @@ class nsFrameLoader final : public nsStubMutationObserver,
               nsIContentSecurityPolicy** aCsp);
 
   // Properly retrieves documentSize of any subdocument type.
-  nsresult GetWindowDimensions(nsIntRect& aRect);
+  nsresult GetWindowDimensions(mozilla::LayoutDeviceIntRect& aRect);
 
   virtual mozilla::dom::ProcessMessageManager* GetProcessMessageManager()
       const override;
@@ -523,7 +523,7 @@ class nsFrameLoader final : public nsStubMutationObserver,
   RefPtr<nsDocShell> mDocShell;
 
   // Holds the last known size of the frame.
-  mozilla::ScreenIntSize mLazySize;
+  mozilla::LayoutDeviceIntSize mLazySize;
 
   // Actor for collecting session store data from content children. This will be
   // cleared and set to null eagerly when taking down the frameloader to break
diff --git a/dom/ipc/BrowserBridgeHost.cpp b/dom/ipc/BrowserBridgeHost.cpp
index 2cb8decd58b8..91b23f695111 100644
--- a/dom/ipc/BrowserBridgeHost.cpp
+++ b/dom/ipc/BrowserBridgeHost.cpp
@@ -66,8 +66,8 @@ bool BrowserBridgeHost::Show(const OwnerShowInfo& aShowInfo) {
   return true;
 }
 
-void BrowserBridgeHost::UpdateDimensions(const nsIntRect& aRect,
-                                         const ScreenIntSize& aSize) {
+void BrowserBridgeHost::UpdateDimensions(const LayoutDeviceIntRect& aRect,
+                                         const LayoutDeviceIntSize& aSize) {
   Unused << mBridge->SendUpdateDimensions(aRect, aSize);
 }
 
diff --git a/dom/ipc/BrowserBridgeHost.h b/dom/ipc/BrowserBridgeHost.h
index 09f2f4dfdd06..6d2a6a801b8f 100644
--- a/dom/ipc/BrowserBridgeHost.h
+++ b/dom/ipc/BrowserBridgeHost.h
@@ -21,7 +21,7 @@ namespace mozilla::dom {
  * See `dom/docs/Fission-IPC-Diagram.svg` for an overview of the DOM IPC
  * actors.
  */
-class BrowserBridgeHost : public RemoteBrowser {
+class BrowserBridgeHost final : public RemoteBrowser {
  public:
   typedef mozilla::layers::LayersId LayersId;
 
@@ -48,8 +48,8 @@ class BrowserBridgeHost : public RemoteBrowser {
   void DestroyComplete() override;
 
   bool Show(const OwnerShowInfo&) override;
-  void UpdateDimensions(const nsIntRect& aRect,
-                        const ScreenIntSize& aSize) override;
+  void UpdateDimensions(const LayoutDeviceIntRect& aRect,
+                        const LayoutDeviceIntSize& aSize) override;
 
   void UpdateEffects(EffectsInfo aInfo) override;
 
diff --git a/dom/ipc/BrowserBridgeParent.cpp b/dom/ipc/BrowserBridgeParent.cpp
index 2bf4d4e5d455..736ea9e9e28f 100644
--- a/dom/ipc/BrowserBridgeParent.cpp
+++ b/dom/ipc/BrowserBridgeParent.cpp
@@ -180,7 +180,7 @@ IPCResult BrowserBridgeParent::RecvResumeLoad(uint64_t aPendingSwitchID) {
 }
 
 IPCResult BrowserBridgeParent::RecvUpdateDimensions(
-    const nsIntRect& aRect, const ScreenIntSize& aSize) {
+    const LayoutDeviceIntRect& aRect, const LayoutDeviceIntSize& aSize) {
   mBrowserParent->UpdateDimensions(aRect, aSize);
   return IPC_OK();
 }
diff --git a/dom/ipc/BrowserBridgeParent.h b/dom/ipc/BrowserBridgeParent.h
index 35dfd7636fe5..f36f9ec330ec 100644
--- a/dom/ipc/BrowserBridgeParent.h
+++ b/dom/ipc/BrowserBridgeParent.h
@@ -76,8 +76,8 @@ class BrowserBridgeParent : public PBrowserBridgeParent {
   mozilla::ipc::IPCResult RecvScrollbarPreferenceChanged(ScrollbarPreference);
   mozilla::ipc::IPCResult RecvLoadURL(nsDocShellLoadState* aLoadState);
   mozilla::ipc::IPCResult RecvResumeLoad(uint64_t aPendingSwitchID);
-  mozilla::ipc::IPCResult RecvUpdateDimensions(const nsIntRect& aRect,
-                                               const ScreenIntSize& aSize);
+  mozilla::ipc::IPCResult RecvUpdateDimensions(
+      const LayoutDeviceIntRect& aRect, const LayoutDeviceIntSize& aSize);
   mozilla::ipc::IPCResult RecvUpdateEffects(const EffectsInfo& aEffects);
   mozilla::ipc::IPCResult RecvUpdateRemotePrintSettings(
       const embedding::PrintData&);
diff --git a/dom/ipc/BrowserChild.cpp b/dom/ipc/BrowserChild.cpp
index 786113675800..db70b19a2fa3 100644
--- a/dom/ipc/BrowserChild.cpp
+++ b/dom/ipc/BrowserChild.cpp
@@ -28,6 +28,7 @@
 #include "mozilla/IMEStateManager.h"
 #include "mozilla/LookAndFeel.h"
 #include "mozilla/MouseEvents.h"
+#include "mozilla/widget/ScreenManager.h"
 #include "mozilla/NativeKeyBindingsType.h"
 #include "mozilla/NullPrincipal.h"
 #include "mozilla/PointerLockManager.h"
@@ -604,7 +605,7 @@ BrowserChild::SetDimensions(DimensionRequest&& aRequest) {
 NS_IMETHODIMP
 BrowserChild::GetDimensions(DimensionKind aDimensionKind, int32_t* aX,
                             int32_t* aY, int32_t* aCx, int32_t* aCy) {
-  ScreenIntRect rect = GetOuterRect();
+  LayoutDeviceIntRect rect = GetOuterRect();
   if (aDimensionKind == DimensionKind::Inner) {
     if (aX || aY) {
       return NS_ERROR_NOT_IMPLEMENTED;
@@ -1007,7 +1008,7 @@ mozilla::ipc::IPCResult BrowserChild::RecvUpdateRemotePrintSettings(
 }
 
 void BrowserChild::DoFakeShow(const ParentShowInfo& aParentShowInfo) {
-  OwnerShowInfo ownerInfo{ScreenIntSize(), ScrollbarPreference::Auto,
+  OwnerShowInfo ownerInfo{LayoutDeviceIntSize(), ScrollbarPreference::Auto,
                           nsSizeMode_Normal};
   RecvShow(aParentShowInfo, ownerInfo);
   mDidFakeShow = true;
@@ -1125,20 +1126,20 @@ mozilla::ipc::IPCResult BrowserChild::RecvUpdateDimensions(
     mHasValidInnerSize = true;
   }
 
-  ScreenIntSize screenSize = GetInnerSize();
-  ScreenIntRect screenRect = GetOuterRect();
-
+  const LayoutDeviceIntSize innerSize = GetInnerSize();
   // Make sure to set the size on the document viewer first.  The
   // MobileViewportManager needs the content viewer size to be updated before
   // the reflow, otherwise it gets a stale size when it computes a new CSS
   // viewport.
   nsCOMPtr<nsIBaseWindow> baseWin = do_QueryInterface(WebNavigation());
-  baseWin->SetPositionAndSize(0, 0, screenSize.width, screenSize.height,
+  baseWin->SetPositionAndSize(0, 0, innerSize.width, innerSize.height,
                               nsIBaseWindow::eRepaint);
 
-  mPuppetWidget->Resize(screenRect.x + mClientOffset.x + mChromeOffset.x,
-                        screenRect.y + mClientOffset.y + mChromeOffset.y,
-                        screenSize.width, screenSize.height, true);
+  const LayoutDeviceIntRect outerRect =
+      GetOuterRect() + mClientOffset + mChromeOffset;
+
+  mPuppetWidget->Resize(outerRect.x, outerRect.y, innerSize.width,
+                        innerSize.height, true);
 
   RecvSafeAreaInsetsChanged(mPuppetWidget->GetSafeAreaInsets());
 
@@ -3345,23 +3346,22 @@ void BrowserChild::NotifyJankedAnimations(
 
 mozilla::ipc::IPCResult BrowserChild::RecvUIResolutionChanged(
     const float& aDpi, const int32_t& aRounding, const double& aScale) {
-  ScreenIntSize oldScreenSize = GetInnerSize();
+  const LayoutDeviceIntSize oldInnerSize = GetInnerSize();
   if (aDpi > 0) {
     mPuppetWidget->UpdateBackingScaleCache(aDpi, aRounding, aScale);
   }
 
-  ScreenIntSize screenSize = GetInnerSize();
-  if (mHasValidInnerSize && oldScreenSize != screenSize) {
-    ScreenIntRect screenRect = GetOuterRect();
-
+  const LayoutDeviceIntSize innerSize = GetInnerSize();
+  if (mHasValidInnerSize && oldInnerSize != innerSize) {
     // See RecvUpdateDimensions for the order of these operations.
     nsCOMPtr<nsIBaseWindow> baseWin = do_QueryInterface(WebNavigation());
-    baseWin->SetPositionAndSize(0, 0, screenSize.width, screenSize.height,
+    baseWin->SetPositionAndSize(0, 0, innerSize.width, innerSize.height,
                                 nsIBaseWindow::eRepaint);
 
-    mPuppetWidget->Resize(screenRect.x + mClientOffset.x + mChromeOffset.x,
-                          screenRect.y + mClientOffset.y + mChromeOffset.y,
-                          screenSize.width, screenSize.height, true);
+    const LayoutDeviceIntRect outerRect =
+        GetOuterRect() + mClientOffset + mChromeOffset;
+    mPuppetWidget->Resize(outerRect.x, outerRect.y, innerSize.width,
+                          innerSize.height, true);
   }
 
   nsCOMPtr<Document> document(GetTopLevelDocument());
@@ -3375,32 +3375,23 @@ mozilla::ipc::IPCResult BrowserChild::RecvUIResolutionChanged(
 }
 
 mozilla::ipc::IPCResult BrowserChild::RecvSafeAreaInsetsChanged(
-    const mozilla::ScreenIntMargin& aSafeAreaInsets) {
+    const mozilla::LayoutDeviceIntMargin& aSafeAreaInsets) {
   mPuppetWidget->UpdateSafeAreaInsets(aSafeAreaInsets);
 
-  nsCOMPtr<nsIScreenManager> screenMgr =
-      do_GetService("@mozilla.org/gfx/screenmanager;1");
-  ScreenIntMargin currentSafeAreaInsets;
-  if (screenMgr) {
-    // aSafeAreaInsets is for current screen. But we have to calculate
-    // safe insets for content window.
-    int32_t x, y, cx, cy;
-    GetDimensions(DimensionKind::Outer, &x, &y, &cx, &cy);
-    nsCOMPtr<nsIScreen> screen;
-    screenMgr->ScreenForRect(x, y, cx, cy, getter_AddRefs(screen));
-
-    if (screen) {
-      LayoutDeviceIntRect windowRect(x + mClientOffset.x + mChromeOffset.x,
-                                     y + mClientOffset.y + mChromeOffset.y, cx,
-                                     cy);
-      currentSafeAreaInsets = nsContentUtils::GetWindowSafeAreaInsets(
-          screen, aSafeAreaInsets, windowRect);
-    }
+  LayoutDeviceIntMargin currentSafeAreaInsets;
+  // aSafeAreaInsets is for current screen. But we have to calculate safe insets
+  // for content window.
+  LayoutDeviceIntRect outerRect = GetOuterRect();
+  RefPtr<Screen> screen = widget::ScreenManager::GetSingleton().ScreenForRect(
+      RoundedToInt(outerRect / mPuppetWidget->GetDesktopToDeviceScale()));
+  if (screen) {
+    LayoutDeviceIntRect windowRect = outerRect + mClientOffset + mChromeOffset;
+    currentSafeAreaInsets = nsContentUtils::GetWindowSafeAreaInsets(
+        screen, aSafeAreaInsets, windowRect);
   }
 
   if (nsCOMPtr<Document> document = GetTopLevelDocument()) {
-    nsPresContext* presContext = document->GetPresContext();
-    if (presContext) {
+    if (nsPresContext* presContext = document->GetPresContext()) {
       presContext->SetSafeAreaInsets(currentSafeAreaInsets);
     }
   }
@@ -3441,11 +3432,8 @@ bool BrowserChild::DeallocPPaymentRequestChild(PPaymentRequestChild* actor) {
   return true;
 }
 
-ScreenIntSize BrowserChild::GetInnerSize() {
-  LayoutDeviceIntSize innerSize =
-      RoundedToInt(mUnscaledInnerSize * mPuppetWidget->GetDefaultScale());
-  return ViewAs<ScreenPixel>(
-      innerSize, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
+LayoutDeviceIntSize BrowserChild::GetInnerSize() {
+  return RoundedToInt(mUnscaledInnerSize * mPuppetWidget->GetDefaultScale());
 };
 
 Maybe<nsRect> BrowserChild::GetVisibleRect() const {
@@ -3489,11 +3477,8 @@ BrowserChild::GetTopLevelViewportVisibleRectInSelfCoords() const {
   return rect;
 }
 
-ScreenIntRect BrowserChild::GetOuterRect() {
-  LayoutDeviceIntRect outerRect =
-      RoundedToInt(mUnscaledOuterRect * mPuppetWidget->GetDefaultScale());
-  return ViewAs<ScreenPixel>(
-      outerRect, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
+LayoutDeviceIntRect BrowserChild::GetOuterRect() {
+  return RoundedToInt(mUnscaledOuterRect * mPuppetWidget->GetDefaultScale());
 }
 
 void BrowserChild::PaintWhileInterruptingJS() {
diff --git a/dom/ipc/BrowserChild.h b/dom/ipc/BrowserChild.h
index 94d7987fbbb7..27767514c1d8 100644
--- a/dom/ipc/BrowserChild.h
+++ b/dom/ipc/BrowserChild.h
@@ -436,7 +436,7 @@ class BrowserChild final : public nsMessageManagerScriptExecutor,
       const IPCTabContext& aContext);
 
   mozilla::ipc::IPCResult RecvSafeAreaInsetsChanged(
-      const mozilla::ScreenIntMargin& aSafeAreaInsets);
+      const mozilla::LayoutDeviceIntMargin& aSafeAreaInsets);
 
 #ifdef ACCESSIBILITY
   PDocAccessibleChild* AllocPDocAccessibleChild(
@@ -568,7 +568,7 @@ class BrowserChild final : public nsMessageManagerScriptExecutor,
   const mozilla::layers::CompositorOptions& GetCompositorOptions() const;
   bool AsyncPanZoomEnabled() const;
 
-  ScreenIntSize GetInnerSize();
+  LayoutDeviceIntSize GetInnerSize();
   CSSSize GetUnscaledInnerSize() { return mUnscaledInnerSize; }
 
   Maybe<nsRect> GetVisibleRect() const;
@@ -758,7 +758,7 @@ class BrowserChild final : public nsMessageManagerScriptExecutor,
 
   bool HasValidInnerSize();
 
-  ScreenIntRect GetOuterRect();
+  LayoutDeviceIntRect GetOuterRect();
 
   void SetUnscaledInnerSize(const CSSSize& aSize) {
     mUnscaledInnerSize = aSize;
diff --git a/dom/ipc/BrowserHost.cpp b/dom/ipc/BrowserHost.cpp
index 489f07a612e5..123c9de9def3 100644
--- a/dom/ipc/BrowserHost.cpp
+++ b/dom/ipc/BrowserHost.cpp
@@ -90,8 +90,8 @@ bool BrowserHost::Show(const OwnerShowInfo& aShowInfo) {
   return mRoot->Show(aShowInfo);
 }
 
-void BrowserHost::UpdateDimensions(const nsIntRect& aRect,
-                                   const ScreenIntSize& aSize) {
+void BrowserHost::UpdateDimensions(const LayoutDeviceIntRect& aRect,
+                                   const LayoutDeviceIntSize& aSize) {
   mRoot->UpdateDimensions(aRect, aSize);
 }
 
diff --git a/dom/ipc/BrowserHost.h b/dom/ipc/BrowserHost.h
index 5b651a1df041..84357d626ba2 100644
--- a/dom/ipc/BrowserHost.h
+++ b/dom/ipc/BrowserHost.h
@@ -87,8 +87,8 @@ class BrowserHost : public RemoteBrowser,
   void DestroyComplete() override;
 
   bool Show(const OwnerShowInfo&) override;
-  void UpdateDimensions(const nsIntRect& aRect,
-                        const ScreenIntSize& aSize) override;
+  void UpdateDimensions(const LayoutDeviceIntRect& aRect,
+                        const LayoutDeviceIntSize& aSize) override;
 
   void UpdateEffects(EffectsInfo aInfo) override;
 
diff --git a/dom/ipc/BrowserParent.cpp b/dom/ipc/BrowserParent.cpp
index eb65fe4730e1..8461e290d9c7 100644
--- a/dom/ipc/BrowserParent.cpp
+++ b/dom/ipc/BrowserParent.cpp
@@ -1027,8 +1027,7 @@ void BrowserParent::InitRendering() {
 
   RefPtr<nsIWidget> widget = GetTopLevelWidget();
   if (widget) {
-    ScreenIntMargin safeAreaInsets = widget->GetSafeAreaInsets();
-    Unused << SendSafeAreaInsetsChanged(safeAreaInsets);
+    Unused << SendSafeAreaInsetsChanged(widget->GetSafeAreaInsets());
   }
 
 #if defined(MOZ_WIDGET_ANDROID)
@@ -1116,7 +1115,7 @@ nsresult BrowserParent::UpdatePosition() {
   if (!frameLoader) {
     return NS_OK;
   }
-  nsIntRect windowDims;
+  LayoutDeviceIntRect windowDims;
   NS_ENSURE_SUCCESS(frameLoader->GetWindowDimensions(windowDims),
                     NS_ERROR_FAILURE);
   // Avoid updating sizes here.
@@ -1139,8 +1138,8 @@ void BrowserParent::NotifyPositionUpdatedForContentsInPopup() {
   }
 }
 
-void BrowserParent::UpdateDimensions(const nsIntRect& rect,
-                                     const ScreenIntSize& size) {
+void BrowserParent::UpdateDimensions(const LayoutDeviceIntRect& rect,
+                                     const LayoutDeviceIntSize& size) {
   if (mIsDestroyed) {
     return;
   }
@@ -1169,26 +1168,18 @@ void BrowserParent::UpdateDimensions(const nsIntRect& rect,
 }
 
 DimensionInfo BrowserParent::GetDimensionInfo() {
-  LayoutDeviceIntRect devicePixelRect = ViewAs<LayoutDevicePixel>(
-      mRect, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
-  LayoutDeviceIntSize devicePixelSize = ViewAs<LayoutDevicePixel>(
-      mDimensions, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
-
-  CSSRect unscaledRect = devicePixelRect / mDefaultScale;
-  CSSSize unscaledSize = devicePixelSize / mDefaultScale;
-  DimensionInfo di(unscaledRect, unscaledSize, mClientOffset, mChromeOffset);
-  return di;
+  CSSRect unscaledRect = mRect / mDefaultScale;
+  CSSSize unscaledSize = mDimensions / mDefaultScale;
+  return DimensionInfo(unscaledRect, unscaledSize, mClientOffset,
+                       mChromeOffset);
 }
 
 void BrowserParent::UpdateNativePointerLockCenter(nsIWidget* aWidget) {
   if (!mLockedNativePointer) {
     return;
   }
-  LayoutDeviceIntRect dims(
-      {0, 0},
-      ViewAs<LayoutDevicePixel>(
-          mDimensions, PixelCastJustification::LayoutDeviceIsScreenForTabDims));
-  aWidget->SetNativePointerLockCenter((dims + mChromeOffset).Center());
+  aWidget->SetNativePointerLockCenter(
+      LayoutDeviceIntRect(mChromeOffset, mDimensions).Center());
 }
 
 void BrowserParent::SizeModeChanged(const nsSizeMode& aSizeMode) {
diff --git a/dom/ipc/BrowserParent.h b/dom/ipc/BrowserParent.h
index 58dee684f464..52cbf24e5883 100644
--- a/dom/ipc/BrowserParent.h
+++ b/dom/ipc/BrowserParent.h
@@ -468,7 +468,8 @@ class BrowserParent final : public PBrowserParent,
 
   bool Show(const OwnerShowInfo&);
 
-  void UpdateDimensions(const nsIntRect& aRect, const ScreenIntSize& aSize);
+  void UpdateDimensions(const LayoutDeviceIntRect& aRect,
+                        const LayoutDeviceIntSize& aSize);
 
   DimensionInfo GetDimensionInfo();
 
@@ -922,8 +923,8 @@ class BrowserParent final : public PBrowserParent,
   };
   nsTArray<SentKeyEventData> mWaitingReplyKeyboardEvents;
 
-  nsIntRect mRect;
-  ScreenIntSize mDimensions;
+  LayoutDeviceIntRect mRect;
+  LayoutDeviceIntSize mDimensions;
   float mDPI;
   int32_t mRounding;
   CSSToLayoutDeviceScale mDefaultScale;
diff --git a/dom/ipc/DOMTypes.ipdlh b/dom/ipc/DOMTypes.ipdlh
index ed72af20dd23..8abdce68b21d 100644
--- a/dom/ipc/DOMTypes.ipdlh
+++ b/dom/ipc/DOMTypes.ipdlh
@@ -39,7 +39,7 @@ using mozilla::DesktopToLayoutDeviceScale from "Units.h";
 using mozilla::CSSToLayoutDeviceScale from "Units.h";
 using mozilla::CSSRect from "Units.h";
 using mozilla::CSSSize from "Units.h";
-using mozilla::ScreenIntSize from "Units.h";
+using mozilla::LayoutDeviceIntSize from "Units.h";
 using mozilla::LayoutDeviceIntPoint from "Units.h";
 using mozilla::ImageIntSize from "Units.h";
 using nsSizeMode from "nsIWidgetListener.h";
@@ -315,7 +315,7 @@ struct ParentShowInfo
 struct OwnerShowInfo {
   // This can be an IntSize rather than a Rect because content processes always
   // render to a virtual <0, 0> top-left point.
-  ScreenIntSize size;
+  LayoutDeviceIntSize size;
 
   // TODO(emilio): Margin preferences go here.
   ScrollbarPreference scrollbarPreference;
diff --git a/dom/ipc/PBrowser.ipdl b/dom/ipc/PBrowser.ipdl
index 14406ad0a6cc..83cf929bb349 100644
--- a/dom/ipc/PBrowser.ipdl
+++ b/dom/ipc/PBrowser.ipdl
@@ -48,9 +48,8 @@ using mozilla::gfx::Matrix4x4 from "mozilla/gfx/Matrix.h";
 using mozilla::gfx::SurfaceFormat from "mozilla/gfx/Types.h";
 using mozilla::LayoutDeviceIntPoint from "Units.h";
 using mozilla::LayoutDevicePoint from "Units.h";
+using mozilla::LayoutDeviceIntMargin from "Units.h";
 using mozilla::ScreenIntCoord from "Units.h";
-using mozilla::ScreenIntMargin from "Units.h";
-using mozilla::ScreenIntPoint from "Units.h";
 using mozilla::ScreenRect from "Units.h";
 using struct mozilla::layers::ScrollableLayerGuid from "mozilla/layers/ScrollableLayerGuid.h";
 using struct mozilla::layers::ZoomConstraints from "mozilla/layers/ZoomConstraints.h";
@@ -936,7 +935,7 @@ child:
      * Tell the child that the safe area of widget has changed.
      *
      */
-    async SafeAreaInsetsChanged(ScreenIntMargin aSafeAreaInsets);
+    async SafeAreaInsetsChanged(LayoutDeviceIntMargin aSafeAreaInsets);
 
     /**
      * Tell the browser that its frame loader has been swapped
diff --git a/dom/ipc/PBrowserBridge.ipdl b/dom/ipc/PBrowserBridge.ipdl
index c2af10d2a49b..a95951393e46 100644
--- a/dom/ipc/PBrowserBridge.ipdl
+++ b/dom/ipc/PBrowserBridge.ipdl
@@ -23,7 +23,6 @@ using mozilla::ScrollAxis from "mozilla/PresShellForwards.h";
 using mozilla::ScrollFlags from "mozilla/PresShellForwards.h";
 using struct nsRect from "nsRect.h";
 using mozilla::dom::CallerType from "mozilla/dom/BindingDeclarations.h";
-using nsIntRect from "nsRect.h";
 using mozilla::dom::EmbedderElementEventType from "mozilla/dom/TabMessageTypes.h";
 [RefCounted] using class nsDocShellLoadState from "nsDocShellLoadState.h";
 using mozilla::IntrinsicSize from "nsIFrame.h";
@@ -92,7 +91,7 @@ parent:
   // Out of process rendering.
   async Show(OwnerShowInfo info);
   async ScrollbarPreferenceChanged(ScrollbarPreference pref);
-  [Compress=all] async UpdateDimensions(nsIntRect rect, ScreenIntSize size);
+  [Compress=all] async UpdateDimensions(LayoutDeviceIntRect rect, LayoutDeviceIntSize size);
   async RenderLayers(bool aEnabled);
 
   async UpdateEffects(EffectsInfo aEffects);
diff --git a/dom/ipc/RemoteBrowser.h b/dom/ipc/RemoteBrowser.h
index 7ea0b669fdb9..f490086e891a 100644
--- a/dom/ipc/RemoteBrowser.h
+++ b/dom/ipc/RemoteBrowser.h
@@ -61,8 +61,8 @@ class RemoteBrowser : public nsISupports {
   virtual void DestroyComplete() = 0;
 
   virtual bool Show(const OwnerShowInfo&) = 0;
-  virtual void UpdateDimensions(const nsIntRect& aRect,
-                                const ScreenIntSize& aSize) = 0;
+  virtual void UpdateDimensions(const LayoutDeviceIntRect& aRect,
+                                const LayoutDeviceIntSize& aSize) = 0;
 
   virtual void UpdateEffects(EffectsInfo aInfo) = 0;
 };
diff --git a/layout/base/UnitTransforms.h b/layout/base/UnitTransforms.h
index 7bbd0f088f73..78d79eb9fe57 100644
--- a/layout/base/UnitTransforms.h
+++ b/layout/base/UnitTransforms.h
@@ -44,9 +44,6 @@ enum class PixelCastJustification : uint8_t {
   // reference point as a screen point. The reverse is useful when synthetically
   // created WidgetEvents need to be converted back to InputData.
   LayoutDeviceIsScreenForUntransformedEvent,
-  // Similar to LayoutDeviceIsScreenForUntransformedEvent, PBrowser handles
-  // some widget/tab dimension information as the OS does -- in screen units.
-  LayoutDeviceIsScreenForTabDims,
   // A combination of LayoutDeviceIsScreenForBounds and
   // ScreenIsParentLayerForRoot, which is how we're using it.
   LayoutDeviceIsParentLayerForRCDRSF,
diff --git a/layout/base/Units.h b/layout/base/Units.h
index 2285d8c1ba1b..480558fccde9 100644
--- a/layout/base/Units.h
+++ b/layout/base/Units.h
@@ -890,8 +890,8 @@ template <class Src, class Dst>
 gfx::MarginTyped<Dst> operator/(const gfx::MarginTyped<Src>& aMargin,
                                 const gfx::ScaleFactor<Dst, Src>& aScale) {
   return gfx::MarginTyped<Dst>(
-      aMargin.top / aScale.scale, aMargin.right / aScale.scale,
-      aMargin.bottom / aScale.scale, aMargin.left / aScale.scale);
+      aMargin.top.value / aScale.scale, aMargin.right.value / aScale.scale,
+      aMargin.bottom.value / aScale.scale, aMargin.left.value / aScale.scale);
 }
 
 template <class Src, class Dst, class F>
diff --git a/layout/base/nsDocumentViewer.cpp b/layout/base/nsDocumentViewer.cpp
index 2e14057cd2e5..9fdbb3065fc4 100644
--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@@ -740,14 +740,12 @@ nsresult nsDocumentViewer::InitPresentationStuff(bool aDoInitialReflow) {
 
   if (mWindow && mDocument->IsTopLevelContentDocument()) {
     // Set initial safe area insets
-    ScreenIntMargin windowSafeAreaInsets;
+    LayoutDeviceIntMargin windowSafeAreaInsets;
     LayoutDeviceIntRect windowRect = mWindow->GetScreenBounds();
-    nsCOMPtr<nsIScreen> screen = mWindow->GetWidgetScreen();
-    if (screen) {
+    if (nsCOMPtr<nsIScreen> screen = mWindow->GetWidgetScreen()) {
       windowSafeAreaInsets = nsContentUtils::GetWindowSafeAreaInsets(
           screen, mWindow->GetSafeAreaInsets(), windowRect);
     }
-
     mPresContext->SetSafeAreaInsets(windowSafeAreaInsets);
   }
 
diff --git a/layout/base/nsPresContext.cpp b/layout/base/nsPresContext.cpp
index 1c24a15088fa..19ffab5db39b 100644
--- a/layout/base/nsPresContext.cpp
+++ b/layout/base/nsPresContext.cpp
@@ -3204,7 +3204,8 @@ nscoord nsPresContext::GetBimodalDynamicToolbarHeightInAppUnits() const {
              : 0;
 }
 
-void nsPresContext::SetSafeAreaInsets(const ScreenIntMargin& aSafeAreaInsets) {
+void nsPresContext::SetSafeAreaInsets(
+    const LayoutDeviceIntMargin& aSafeAreaInsets) {
   if (mSafeAreaInsets == aSafeAreaInsets) {
     return;
   }
diff --git a/layout/base/nsPresContext.h b/layout/base/nsPresContext.h
index b24336dde554..5c8337bd7d16 100644
--- a/layout/base/nsPresContext.h
+++ b/layout/base/nsPresContext.h
@@ -544,9 +544,11 @@ class nsPresContext : public nsISupports, public mozilla::SupportsWeakPtr {
   /**
    * Notify the pres context that the safe area insets have changed.
    */
-  void SetSafeAreaInsets(const mozilla::ScreenIntMargin& aInsets);
+  void SetSafeAreaInsets(const mozilla::LayoutDeviceIntMargin& aInsets);
 
-  mozilla::ScreenIntMargin GetSafeAreaInsets() const { return mSafeAreaInsets; }
+  const mozilla::LayoutDeviceIntMargin& GetSafeAreaInsets() const {
+    return mSafeAreaInsets;
+  }
 
   void RegisterManagedPostRefreshObserver(mozilla::ManagedPostRefreshObserver*);
   void UnregisterManagedPostRefreshObserver(
@@ -1245,7 +1247,7 @@ class nsPresContext : public nsISupports, public mozilla::SupportsWeakPtr {
   // The software keyboard height.
   mozilla::ScreenIntCoord mKeyboardHeight;
   // Safe area insets support
-  mozilla::ScreenIntMargin mSafeAreaInsets;
+  mozilla::LayoutDeviceIntMargin mSafeAreaInsets;
   nsSize mPageSize;
 
   // The computed page margins from the print settings.
diff --git a/layout/generic/nsSubDocumentFrame.cpp b/layout/generic/nsSubDocumentFrame.cpp
index 1b80b04aa727..9c62a8a1f5c6 100644
--- a/layout/generic/nsSubDocumentFrame.cpp
+++ b/layout/generic/nsSubDocumentFrame.cpp
@@ -283,26 +283,27 @@ nsRect nsSubDocumentFrame::GetDestRect(const nsRect& aConstraintRect) {
       GetIntrinsicRatio(), StylePosition());
 }
 
-ScreenIntSize nsSubDocumentFrame::GetSubdocumentSize() {
+LayoutDeviceIntSize nsSubDocumentFrame::GetSubdocumentSize() {
   if (HasAnyStateBits(NS_FRAME_FIRST_REFLOW)) {
     if (RefPtr<nsFrameLoader> frameloader = FrameLoader()) {
       nsIFrame* detachedFrame = frameloader->GetDetachedSubdocFrame();
       if (nsView* view = detachedFrame ? detachedFrame->GetView() : nullptr) {
         nsSize size = view->GetBounds().Size();
         nsPresContext* presContext = detachedFrame->PresContext();
-        return ScreenIntSize(presContext->AppUnitsToDevPixels(size.width),
-                             presContext->AppUnitsToDevPixels(size.height));
+        return LayoutDeviceIntSize(
+            presContext->AppUnitsToDevPixels(size.width),
+            presContext->AppUnitsToDevPixels(size.height));
       }
     }
     // Pick some default size for now.  Using 10x10 because that's what the
     // code used to do.
-    return ScreenIntSize(10, 10);
+    return LayoutDeviceIntSize(10, 10);
   }
 
   nsSize docSizeAppUnits = GetDestRect().Size();
   nsPresContext* pc = PresContext();
-  return ScreenIntSize(pc->AppUnitsToDevPixels(docSizeAppUnits.width),
-                       pc->AppUnitsToDevPixels(docSizeAppUnits.height));
+  return LayoutDeviceIntSize(pc->AppUnitsToDevPixels(docSizeAppUnits.width),
+                             pc->AppUnitsToDevPixels(docSizeAppUnits.height));
 }
 
 static void WrapBackgroundColorInOwnLayer(nsDisplayListBuilder* aBuilder,
diff --git a/layout/generic/nsSubDocumentFrame.h b/layout/generic/nsSubDocumentFrame.h
index ffadebaba2df..088ae1e775dd 100644
--- a/layout/generic/nsSubDocumentFrame.h
+++ b/layout/generic/nsSubDocumentFrame.h
@@ -103,7 +103,7 @@ class nsSubDocumentFrame final : public nsAtomicContainerFrame,
   mozilla::PresShell* GetSubdocumentPresShellForPainting(uint32_t aFlags);
   nsRect GetDestRect();
   nsRect GetDestRect(const nsRect& aConstraintRect);
-  mozilla::ScreenIntSize GetSubdocumentSize();
+  mozilla::LayoutDeviceIntSize GetSubdocumentSize();
 
   bool ContentReactsToPointerEvents() const;
 
diff --git a/layout/style/GeckoBindings.cpp b/layout/style/GeckoBindings.cpp
index b05727bd1adf..c0f47bfa8b46 100644
--- a/layout/style/GeckoBindings.cpp
+++ b/layout/style/GeckoBindings.cpp
@@ -1664,11 +1664,13 @@ bool Gecko_AssertClassAttrValueIsSane(const nsAttrValue* aValue) {
 void Gecko_GetSafeAreaInsets(const nsPresContext* aPresContext, float* aTop,
                              float* aRight, float* aBottom, float* aLeft) {
   MOZ_ASSERT(aPresContext);
-  ScreenIntMargin safeAreaInsets = aPresContext->GetSafeAreaInsets();
-  *aTop = aPresContext->DevPixelsToFloatCSSPixels(safeAreaInsets.top);
-  *aRight = aPresContext->DevPixelsToFloatCSSPixels(safeAreaInsets.right);
-  *aBottom = aPresContext->DevPixelsToFloatCSSPixels(safeAreaInsets.bottom);
-  *aLeft = aPresContext->DevPixelsToFloatCSSPixels(safeAreaInsets.left);
+  const CSSMargin insets =
+      LayoutDeviceMargin(aPresContext->GetSafeAreaInsets()) /
+      aPresContext->CSSToDevPixelScale();
+  *aTop = insets.top;
+  *aRight = insets.right;
+  *aBottom = insets.bottom;
+  *aLeft = insets.left;
 }
 
 void Gecko_PrintfStderr(const nsCString* aStr) {
diff --git a/view/nsView.cpp b/view/nsView.cpp
index 8506cce03fda..42f6a78fb016 100644
--- a/view/nsView.cpp
+++ b/view/nsView.cpp
@@ -1013,7 +1013,8 @@ nsEventStatus nsView::HandleEvent(WidgetGUIEvent* aEvent,
   return result;
 }
 
-void nsView::SafeAreaInsetsChanged(const ScreenIntMargin& aSafeAreaInsets) {
+void nsView::SafeAreaInsetsChanged(
+    const LayoutDeviceIntMargin& aSafeAreaInsets) {
   if (!IsRoot()) {
     return;
   }
@@ -1023,10 +1024,9 @@ void nsView::SafeAreaInsetsChanged(const ScreenIntMargin& aSafeAreaInsets) {
     return;
   }
 
-  ScreenIntMargin windowSafeAreaInsets;
-  LayoutDeviceIntRect windowRect = mWindow->GetScreenBounds();
-  nsCOMPtr<nsIScreen> screen = mWindow->GetWidgetScreen();
-  if (screen) {
+  LayoutDeviceIntMargin windowSafeAreaInsets;
+  const LayoutDeviceIntRect windowRect = mWindow->GetScreenBounds();
+  if (nsCOMPtr<nsIScreen> screen = mWindow->GetWidgetScreen()) {
     windowSafeAreaInsets = nsContentUtils::GetWindowSafeAreaInsets(
         screen, aSafeAreaInsets, windowRect);
   }
diff --git a/view/nsView.h b/view/nsView.h
index 73acb9273119..37ccb83b2d36 100644
--- a/view/nsView.h
+++ b/view/nsView.h
@@ -408,37 +408,33 @@ class nsView final : public nsIWidgetListener {
   }
 
   // nsIWidgetListener
-  virtual mozilla::PresShell* GetPresShell() override;
-  virtual nsView* GetView() override { return this; }
-  virtual bool WindowMoved(nsIWidget* aWidget, int32_t x, int32_t y,
-                           ByMoveToRect) override;
-  virtual bool WindowResized(nsIWidget* aWidget, int32_t aWidth,
-                             int32_t aHeight) override;
+  mozilla::PresShell* GetPresShell() override;
+  nsView* GetView() override { return this; }
+  bool WindowMoved(nsIWidget* aWidget, int32_t x, int32_t y,
+                   ByMoveToRect) override;
+  bool WindowResized(nsIWidget* aWidget, int32_t aWidth,
+                     int32_t aHeight) override;
 #if defined(MOZ_WIDGET_ANDROID)
-  virtual void DynamicToolbarMaxHeightChanged(
-      mozilla::ScreenIntCoord aHeight) override;
-  virtual void DynamicToolbarOffsetChanged(
-      mozilla::ScreenIntCoord aOffset) override;
-  virtual void KeyboardHeightChanged(mozilla::ScreenIntCoord aHeight) override;
+  void DynamicToolbarMaxHeightChanged(mozilla::ScreenIntCoord aHeight) override;
+  void DynamicToolbarOffsetChanged(mozilla::ScreenIntCoord aOffset) override;
+  void KeyboardHeightChanged(mozilla::ScreenIntCoord aHeight) override;
 #endif
-  virtual bool RequestWindowClose(nsIWidget* aWidget) override;
+  bool RequestWindowClose(nsIWidget* aWidget) override;
   MOZ_CAN_RUN_SCRIPT_BOUNDARY
-  virtual void WillPaintWindow(nsIWidget* aWidget) override;
+  void WillPaintWindow(nsIWidget* aWidget) override;
   MOZ_CAN_RUN_SCRIPT_BOUNDARY
-  virtual bool PaintWindow(nsIWidget* aWidget,
-                           LayoutDeviceIntRegion aRegion) override;
+  bool PaintWindow(nsIWidget* aWidget, LayoutDeviceIntRegion aRegion) override;
   MOZ_CAN_RUN_SCRIPT_BOUNDARY
-  virtual void DidPaintWindow() override;
-  virtual void DidCompositeWindow(
-      mozilla::layers::TransactionId aTransactionId,
-      const mozilla::TimeStamp& aCompositeStart,
-      const mozilla::TimeStamp& aCompositeEnd) override;
-  virtual void RequestRepaint() override;
-  virtual bool ShouldNotBeVisible() override;
+  void DidPaintWindow() override;
+  void DidCompositeWindow(mozilla::layers::TransactionId aTransactionId,
+                          const mozilla::TimeStamp& aCompositeStart,
+                          const mozilla::TimeStamp& aCompositeEnd) override;
+  void RequestRepaint() override;
+  bool ShouldNotBeVisible() override;
   MOZ_CAN_RUN_SCRIPT_BOUNDARY
-  virtual nsEventStatus HandleEvent(mozilla::WidgetGUIEvent* aEvent,
-                                    bool aUseAttachedEvents) override;
-  virtual void SafeAreaInsetsChanged(const mozilla::ScreenIntMargin&) override;
+  nsEventStatus HandleEvent(mozilla::WidgetGUIEvent* aEvent,
+                            bool aUseAttachedEvents) override;
+  void SafeAreaInsetsChanged(const mozilla::LayoutDeviceIntMargin&) override;
 
   virtual ~nsView();
 
diff --git a/widget/PuppetWidget.cpp b/widget/PuppetWidget.cpp
index 80657a2d8ee7..059cdbb03be8 100644
--- a/widget/PuppetWidget.cpp
+++ b/widget/PuppetWidget.cpp
@@ -988,12 +988,12 @@ void PuppetWidget::StartAsyncScrollbarDrag(
   mBrowserChild->StartScrollbarDrag(aDragMetrics);
 }
 
-ScreenIntMargin PuppetWidget::GetSafeAreaInsets() const {
+LayoutDeviceIntMargin PuppetWidget::GetSafeAreaInsets() const {
   return mSafeAreaInsets;
 }
 
 void PuppetWidget::UpdateSafeAreaInsets(
-    const ScreenIntMargin& aSafeAreaInsets) {
+    const LayoutDeviceIntMargin& aSafeAreaInsets) {
   mSafeAreaInsets = aSafeAreaInsets;
 }
 
diff --git a/widget/PuppetWidget.h b/widget/PuppetWidget.h
index f352c329739a..24f093b6341f 100644
--- a/widget/PuppetWidget.h
+++ b/widget/PuppetWidget.h
@@ -204,8 +204,8 @@ class PuppetWidget final : public nsBaseWidget,
   }
 
   // safe area insets support
-  ScreenIntMargin GetSafeAreaInsets() const override;
-  void UpdateSafeAreaInsets(const ScreenIntMargin& aSafeAreaInsets);
+  LayoutDeviceIntMargin GetSafeAreaInsets() const override;
+  void UpdateSafeAreaInsets(const LayoutDeviceIntMargin& aSafeAreaInsets);
 
   // Get the offset to the chrome of the window that this tab belongs to.
   //
@@ -363,8 +363,7 @@ class PuppetWidget final : public nsBaseWidget,
   int32_t mRounding = 1;
   double mDefaultScale = GetFallbackDefaultScale().scale;
 
-  ScreenIntMargin mSafeAreaInsets;
-
+  LayoutDeviceIntMargin mSafeAreaInsets;
   RefPtr<TextEventDispatcherListener> mNativeTextEventDispatcherListener;
 
  protected:
diff --git a/widget/android/nsWindow.cpp b/widget/android/nsWindow.cpp
index 66f03e1bf337..2f0a9d41dfe7 100644
--- a/widget/android/nsWindow.cpp
+++ b/widget/android/nsWindow.cpp
@@ -1747,7 +1747,7 @@ class LayerViewSupport final
       return;
     }
 
-    ScreenIntMargin safeAreaInsets(aTop, aRight, aBottom, aLeft);
+    LayoutDeviceIntMargin safeAreaInsets(aTop, aRight, aBottom, aLeft);
     gkWindow->UpdateSafeAreaInsets(safeAreaInsets);
   }
 };
@@ -3275,9 +3275,12 @@ void nsWindow::KeyboardHeightChanged(ScreenIntCoord aHeight) {
   }
 }
 
-ScreenIntMargin nsWindow::GetSafeAreaInsets() const { return mSafeAreaInsets; }
+LayoutDeviceIntMargin nsWindow::GetSafeAreaInsets() const {
+  return mSafeAreaInsets;
+}
 
-void nsWindow::UpdateSafeAreaInsets(const ScreenIntMargin& aSafeAreaInsets) {
+void nsWindow::UpdateSafeAreaInsets(
+    const LayoutDeviceIntMargin& aSafeAreaInsets) {
   mSafeAreaInsets = aSafeAreaInsets;
 
   if (mWidgetListener) {
diff --git a/widget/android/nsWindow.h b/widget/android/nsWindow.h
index 28bc574cfb7f..0a8b7c8dba4e 100644
--- a/widget/android/nsWindow.h
+++ b/widget/android/nsWindow.h
@@ -73,7 +73,7 @@ class nsWindow final : public nsBaseWidget {
  private:
   nsCOMPtr<nsIUserIdleServiceInternal> mIdleService;
   mozilla::ScreenIntCoord mDynamicToolbarMaxHeight{0};
-  mozilla::ScreenIntMargin mSafeAreaInsets;
+  mozilla::LayoutDeviceIntMargin mSafeAreaInsets;
   mozilla::widget::PlatformCompositorWidgetDelegate* mCompositorWidgetDelegate =
       nullptr;
   mozilla::Mutex mDestroyMutex{"nsWindow::mDestroyMutex"};
@@ -251,8 +251,8 @@ class nsWindow final : public nsBaseWidget {
 
   void UpdateDynamicToolbarOffset(mozilla::ScreenIntCoord aOffset);
 
-  mozilla::ScreenIntMargin GetSafeAreaInsets() const override;
-  void UpdateSafeAreaInsets(const mozilla::ScreenIntMargin& aSafeAreaInsets);
+  mozilla::LayoutDeviceIntMargin GetSafeAreaInsets() const override;
+  void UpdateSafeAreaInsets(const mozilla::LayoutDeviceIntMargin&);
 
   void KeyboardHeightChanged(mozilla::ScreenIntCoord aHeight);
 
diff --git a/widget/nsIBaseWindow.idl b/widget/nsIBaseWindow.idl
index 664facd40eac..b51990e21c2c 100644
--- a/widget/nsIBaseWindow.idl
+++ b/widget/nsIBaseWindow.idl
@@ -173,6 +173,14 @@ interface nsIBaseWindow : nsISupports
    */
   [noscript] void getDimensions(in DimensionKind aDimensionKind, out long aX, out long aY, out long aCX, out long aCY);
 
+%{C++
+  mozilla::LayoutDeviceIntRect GetDimensions(mozilla::DimensionKind aDimensionKind) {
+    int32_t x = 0, y = 0, w = 0, h = 0;
+    GetDimensions(aDimensionKind, &x, &y, &w, &h);
+    return mozilla::LayoutDeviceIntRect(x, y, w, h);
+  }
+%}
+
   /**
    * Tell the window to repaint itself
    * @param aForce - if true, repaint immediately
diff --git a/widget/nsIWidget.h b/widget/nsIWidget.h
index bbadacd8e839..06fd73d819b4 100644
--- a/widget/nsIWidget.h
+++ b/widget/nsIWidget.h
@@ -1667,8 +1667,8 @@ class nsIWidget : public nsISupports {
    * Get safe area insets except to cutout.
    * See https://drafts.csswg.org/css-env-1/#safe-area-insets.
    */
-  virtual mozilla::ScreenIntMargin GetSafeAreaInsets() const {
-    return mozilla::ScreenIntMargin();
+  virtual mozilla::LayoutDeviceIntMargin GetSafeAreaInsets() const {
+    return mozilla::LayoutDeviceIntMargin();
   }
 
  private:
diff --git a/widget/nsIWidgetListener.cpp b/widget/nsIWidgetListener.cpp
index b0e2c438e5ee..ed4609b6d873 100644
--- a/widget/nsIWidgetListener.cpp
+++ b/widget/nsIWidgetListener.cpp
@@ -33,8 +33,8 @@ bool nsIWidgetListener::WindowResized(nsIWidget* aWidget, int32_t aWidth,
 
 void nsIWidgetListener::SizeModeChanged(nsSizeMode aSizeMode) {}
 
-void nsIWidgetListener::SafeAreaInsetsChanged(const mozilla::ScreenIntMargin&) {
-}
+void nsIWidgetListener::SafeAreaInsetsChanged(
+    const mozilla::LayoutDeviceIntMargin&) {}
 
 #if defined(MOZ_WIDGET_ANDROID)
 void nsIWidgetListener::DynamicToolbarMaxHeightChanged(ScreenIntCoord aHeight) {
diff --git a/widget/nsIWidgetListener.h b/widget/nsIWidgetListener.h
index d0d2e334704a..637e4e51640d 100644
--- a/widget/nsIWidgetListener.h
+++ b/widget/nsIWidgetListener.h
@@ -176,7 +176,7 @@ class nsIWidgetListener {
    * Called when safe area insets are changed.
    */
   virtual void SafeAreaInsetsChanged(
-      const mozilla::ScreenIntMargin& aSafeAreaInsets);
+      const mozilla::LayoutDeviceIntMargin& aSafeAreaInsets);
 };
 
 #endif