diff --git a/dom/base/nsFrameLoader.h b/dom/base/nsFrameLoader.h
index 54a0ec50e276..0e02528e77a1 100644
--- a/dom/base/nsFrameLoader.h
+++ b/dom/base/nsFrameLoader.h
@@ -227,6 +227,9 @@ public:
   void ActivateUpdateHitRegion();
   void DeactivateUpdateHitRegion();
 
+  // Properly retrieves documentSize of any subdocument type.
+  nsresult GetWindowDimensions(nsIntRect& aRect);
+
 private:
 
   void SetOwnerContent(mozilla::dom::Element* aContent);
@@ -282,9 +285,6 @@ private:
   nsresult MaybeCreateDocShell();
   nsresult EnsureMessageManager();
 
-  // Properly retrieves documentSize of any subdocument type.
-  nsresult GetWindowDimensions(nsIntRect& aRect);
-
   // Updates the subdocument position and size. This gets called only
   // when we have our own in-process DocShell.
   void UpdateBaseWindowPositionAndSize(nsSubDocumentFrame *aIFrame);
diff --git a/dom/ipc/TabParent.cpp b/dom/ipc/TabParent.cpp
index 094e2a3b7a10..15569ce23612 100644
--- a/dom/ipc/TabParent.cpp
+++ b/dom/ipc/TabParent.cpp
@@ -80,6 +80,7 @@
 #include "nsICancelable.h"
 #include "gfxPrefs.h"
 #include "nsILoginManagerPrompter.h"
+#include "nsPIWindowRoot.h"
 #include <algorithm>
 
 using namespace mozilla::dom;
@@ -321,7 +322,27 @@ TabParent::RemoveTabParentFromTable(uint64_t aLayersId)
 void
 TabParent::SetOwnerElement(Element* aElement)
 {
+  // If we held previous content then unregister for its events.
+  if (mFrameElement && mFrameElement->OwnerDoc()->GetWindow()) {
+    nsCOMPtr<nsPIDOMWindow> window = mFrameElement->OwnerDoc()->GetWindow();
+    nsCOMPtr<EventTarget> eventTarget = window->GetTopWindowRoot();
+    if (eventTarget) {
+      eventTarget->RemoveEventListener(NS_LITERAL_STRING("MozUpdateWindowPos"),
+                                       this, false);
+    }
+  }
+
+  // Update to the new content, and register to listen for events from it.
   mFrameElement = aElement;
+  if (mFrameElement && mFrameElement->OwnerDoc()->GetWindow()) {
+    nsCOMPtr<nsPIDOMWindow> window = mFrameElement->OwnerDoc()->GetWindow();
+    nsCOMPtr<EventTarget> eventTarget = window->GetTopWindowRoot();
+    if (eventTarget) {
+      eventTarget->AddEventListener(NS_LITERAL_STRING("MozUpdateWindowPos"),
+                                    this, false, false);
+    }
+  }
+
   TryCacheDPIAndScale();
 }
 
@@ -357,6 +378,8 @@ TabParent::Destroy()
     return;
   }
 
+  SetOwnerElement(nullptr);
+
   // If this fails, it's most likely due to a content-process crash,
   // and auto-cleanup will kick in.  Otherwise, the child side will
   // destroy itself and send back __delete__().
@@ -900,8 +923,9 @@ TabParent::UpdateDimensions(const nsIntRect& rect, const nsIntSize& size,
     mRect = rect;
     mDimensions = size;
     mOrientation = orientation;
+    mChromeDisp = aChromeDisp;
 
-    unused << SendUpdateDimensions(mRect, mDimensions, mOrientation, aChromeDisp);
+    unused << SendUpdateDimensions(mRect, mDimensions, mOrientation, mChromeDisp);
   }
 }
 
@@ -2668,6 +2692,27 @@ TabParent::DeallocPPluginWidgetParent(mozilla::plugins::PPluginWidgetParent* aAc
   return true;
 }
 
+nsresult
+TabParent::HandleEvent(nsIDOMEvent* aEvent)
+{
+  nsAutoString eventType;
+  aEvent->GetType(eventType);
+
+  if (eventType.EqualsLiteral("MozUpdateWindowPos")) {
+    // This event is sent when the widget moved.  Therefore we only update
+    // the position.
+    nsRefPtr<nsFrameLoader> frameLoader = GetFrameLoader();
+    if (!frameLoader) {
+      return NS_OK;
+    }
+    nsIntRect windowDims;
+    NS_ENSURE_SUCCESS(frameLoader->GetWindowDimensions(windowDims), NS_ERROR_FAILURE);
+    UpdateDimensions(windowDims, mDimensions, mChromeDisp);
+    return NS_OK;
+  }
+  return NS_OK;
+}
+
 class FakeChannel MOZ_FINAL : public nsIChannel,
                               public nsIAuthPromptCallback,
                               public nsIInterfaceRequestor,
diff --git a/dom/ipc/TabParent.h b/dom/ipc/TabParent.h
index f8c49232e8fb..63e2cc51aef9 100644
--- a/dom/ipc/TabParent.h
+++ b/dom/ipc/TabParent.h
@@ -22,6 +22,7 @@
 #include "Units.h"
 #include "WritingModes.h"
 #include "js/TypeDecls.h"
+#include "nsIDOMEventListener.h"
 
 class nsFrameLoader;
 class nsIFrameLoader;
@@ -58,7 +59,8 @@ class nsIContentParent;
 class Element;
 struct StructuredCloneData;
 
-class TabParent : public PBrowserParent 
+class TabParent : public PBrowserParent
+                , public nsIDOMEventListener
                 , public nsITabParent 
                 , public nsIAuthPromptProvider
                 , public nsISecureBrowserUI
@@ -99,6 +101,9 @@ public:
         mBrowserDOMWindow = aBrowserDOMWindow;
     }
 
+    // nsIDOMEventListener interfaces 
+    NS_DECL_NSIDOMEVENTLISTENER
+
     already_AddRefed<nsILoadContext> GetLoadContext();
 
     nsIXULBrowserWindow* GetXULBrowserWindow();
@@ -440,6 +445,7 @@ protected:
     nsIntRect mRect;
     nsIntSize mDimensions;
     ScreenOrientation mOrientation;
+    nsIntPoint mChromeDisp;
     float mDPI;
     CSSToLayoutDeviceScale mDefaultScale;
     bool mShown;
diff --git a/xpfe/appshell/nsWebShellWindow.cpp b/xpfe/appshell/nsWebShellWindow.cpp
index 29dde6155d25..4c6632f680ea 100644
--- a/xpfe/appshell/nsWebShellWindow.cpp
+++ b/xpfe/appshell/nsWebShellWindow.cpp
@@ -71,6 +71,8 @@
 #include "mozilla/DebugOnly.h"
 #include "mozilla/MouseEvents.h"
 
+#include "nsPIWindowRoot.h"
+
 #ifdef XP_MACOSX
 #include "nsINativeMenuService.h"
 #define USE_NATIVE_MENUS
@@ -257,6 +259,15 @@ nsWebShellWindow::WindowMoved(nsIWidget* aWidget, int32_t x, int32_t y)
     pm->AdjustPopupsOnWindowChange(window);
   }
 
+  // Notify all tabs that the widget moved.
+  if (mDocShell && mDocShell->GetWindow()) {
+    nsCOMPtr<EventTarget> eventTarget = mDocShell->GetWindow()->GetTopWindowRoot();
+    nsContentUtils::DispatchChromeEvent(mDocShell->GetDocument(),
+                                        eventTarget,
+                                        NS_LITERAL_STRING("MozUpdateWindowPos"),
+                                        false, false, nullptr);
+  }
+
   // Persist position, but not immediately, in case this OS is firing
   // repeated move events as the user drags the window
   SetPersistenceTimer(PAD_POSITION);