diff --git a/content/base/src/nsFrameLoader.cpp b/content/base/src/nsFrameLoader.cpp
index 82a493ac87c..d53eca5446f 100644
--- a/content/base/src/nsFrameLoader.cpp
+++ b/content/base/src/nsFrameLoader.cpp
@@ -1021,7 +1021,7 @@ nsFrameLoader::ShowRemoteFrame(const nsIntSize& size,
       mRemoteBrowserInitialized = true;
     }
   } else {
-    nsRect dimensions;
+    nsIntRect dimensions;
     NS_ENSURE_SUCCESS(GetWindowDimensions(dimensions), false);
 
     // Don't show remote iframe if we are waiting for the completion of reflow.
@@ -1877,7 +1877,7 @@ nsFrameLoader::CheckForRecursiveLoad(nsIURI* aURI)
 }
 
 nsresult
-nsFrameLoader::GetWindowDimensions(nsRect& aRect)
+nsFrameLoader::GetWindowDimensions(nsIntRect& aRect)
 {
   // Need to get outer window position here
   nsIDocument* doc = mOwnerContent->GetDocument();
@@ -1917,7 +1917,7 @@ nsFrameLoader::UpdatePositionAndSize(nsSubDocumentFrame *aIFrame)
   if (mRemoteFrame) {
     if (mRemoteBrowser) {
       nsIntSize size = aIFrame->GetSubdocumentSize();
-      nsRect dimensions;
+      nsIntRect dimensions;
       NS_ENSURE_SUCCESS(GetWindowDimensions(dimensions), NS_ERROR_FAILURE);
       mRemoteBrowser->UpdateDimensions(dimensions, size);
     }
diff --git a/content/base/src/nsFrameLoader.h b/content/base/src/nsFrameLoader.h
index 08a05914573..6384b4b499e 100644
--- a/content/base/src/nsFrameLoader.h
+++ b/content/base/src/nsFrameLoader.h
@@ -370,7 +370,7 @@ private:
   nsresult EnsureMessageManager();
 
   // Properly retrieves documentSize of any subdocument type.
-  nsresult GetWindowDimensions(nsRect& aRect);
+  nsresult GetWindowDimensions(nsIntRect& aRect);
 
   // Updates the subdocument position and size. This gets called only
   // when we have our own in-process DocShell.
diff --git a/dom/ipc/PBrowser.ipdl b/dom/ipc/PBrowser.ipdl
index af21e3ca82e..fb24f9d89d2 100644
--- a/dom/ipc/PBrowser.ipdl
+++ b/dom/ipc/PBrowser.ipdl
@@ -406,7 +406,7 @@ child:
 
     CacheFileDescriptor(nsString path, FileDescriptor fd);
 
-    UpdateDimensions(nsRect rect, nsIntSize size, ScreenOrientation orientation) compress;
+    UpdateDimensions(nsIntRect rect, nsIntSize size, ScreenOrientation orientation) compress;
 
     UpdateFrame(FrameMetrics frame);
 
diff --git a/dom/ipc/TabChild.cpp b/dom/ipc/TabChild.cpp
index f7e51bf67b9..2bfed37c7ba 100644
--- a/dom/ipc/TabChild.cpp
+++ b/dom/ipc/TabChild.cpp
@@ -1743,16 +1743,13 @@ TabChild::RecvShow(const nsIntSize& size)
 }
 
 bool
-TabChild::RecvUpdateDimensions(const nsRect& rect, const nsIntSize& size, const ScreenOrientation& orientation)
+TabChild::RecvUpdateDimensions(const nsIntRect& rect, const nsIntSize& size, const ScreenOrientation& orientation)
 {
     if (!mRemoteFrame) {
         return true;
     }
 
-    mOuterRect.x = rect.x;
-    mOuterRect.y = rect.y;
-    mOuterRect.width = rect.width;
-    mOuterRect.height = rect.height;
+    mOuterRect = rect;
 
     bool initialSizing = !HasValidInnerSize()
                       && (size.width != 0 && size.height != 0);
diff --git a/dom/ipc/TabChild.h b/dom/ipc/TabChild.h
index 35447c3a197..ec55dc6a5ef 100644
--- a/dom/ipc/TabChild.h
+++ b/dom/ipc/TabChild.h
@@ -318,7 +318,7 @@ public:
                                          const FileDescriptor& aFileDescriptor)
                                          MOZ_OVERRIDE;
     virtual bool RecvShow(const nsIntSize& size) MOZ_OVERRIDE;
-    virtual bool RecvUpdateDimensions(const nsRect& rect,
+    virtual bool RecvUpdateDimensions(const nsIntRect& rect,
                                       const nsIntSize& size,
                                       const ScreenOrientation& orientation) MOZ_OVERRIDE;
     virtual bool RecvUpdateFrame(const mozilla::layers::FrameMetrics& aFrameMetrics) MOZ_OVERRIDE;
diff --git a/dom/ipc/TabParent.cpp b/dom/ipc/TabParent.cpp
index a5e166ea787..1ec2a3116ff 100644
--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -560,7 +560,7 @@ TabParent::Show(const nsIntSize& size)
 }
 
 void
-TabParent::UpdateDimensions(const nsRect& rect, const nsIntSize& size)
+TabParent::UpdateDimensions(const nsIntRect& rect, const nsIntSize& size)
 {
   if (mIsDestroyed) {
     return;
diff --git a/dom/ipc/TabParent.h b/dom/ipc/TabParent.h
index f7c81ea7105..1ee0c3002b9 100644
--- a/dom/ipc/TabParent.h
+++ b/dom/ipc/TabParent.h
@@ -208,7 +208,7 @@ public:
     // message-sending functions under a layer of indirection and
     // eating the return values
     void Show(const nsIntSize& size);
-    void UpdateDimensions(const nsRect& rect, const nsIntSize& size);
+    void UpdateDimensions(const nsIntRect& rect, const nsIntSize& size);
     void UpdateFrame(const layers::FrameMetrics& aFrameMetrics);
     void UIResolutionChanged();
     void AcknowledgeScrollUpdate(const ViewID& aScrollId, const uint32_t& aScrollGeneration);
@@ -374,7 +374,7 @@ protected:
     // The number of event series we're currently capturing.
     int32_t mEventCaptureDepth;
 
-    nsRect mRect;
+    nsIntRect mRect;
     nsIntSize mDimensions;
     ScreenOrientation mOrientation;
     float mDPI;