--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -5250,17 +5250,18 @@ void PresShell::SynthesizeMouseMove(bool
 
   if (mMouseLocation == nsPoint(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE))
     return;
 
   if (!mSynthMouseMoveEvent.IsPending()) {
     nsRefPtr<nsSynthMouseMoveEvent> ev =
         new nsSynthMouseMoveEvent(this, aFromScroll);
 
-    if (NS_FAILED(NS_DispatchToCurrentThread(ev))) {
+    if (!GetPresContext()->RefreshDriver()->AddRefreshObserver(ev,
+                                                               Flush_Display)) {
       NS_WARNING("failed to dispatch nsSynthMouseMoveEvent");
       return;
     }
 
     mSynthMouseMoveEvent = ev;
   }
 }
 

--- a/layout/base/nsPresShell.h
+++ b/layout/base/nsPresShell.h
@@ -847,27 +847,38 @@ private:
   // the mouse pointer may have changed without the mouse moving (eg scrolling,
   // change to the document contents).
   // It is set only on a presshell for a root document, this value represents
   // the last observed location of the mouse relative to that root document. It
   // is set to (NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE) if the mouse isn't
   // over our window or there is no last observed mouse location for some
   // reason.
   nsPoint mMouseLocation;
-  class nsSynthMouseMoveEvent : public nsRunnable {
+  class nsSynthMouseMoveEvent : public nsARefreshObserver {
   public:
     nsSynthMouseMoveEvent(PresShell* aPresShell, bool aFromScroll)
       : mPresShell(aPresShell), mFromScroll(aFromScroll) {
       NS_ASSERTION(mPresShell, "null parameter");
     }
-    void Revoke() { mPresShell = nsnull; }
-    NS_IMETHOD Run() {
+    ~nsSynthMouseMoveEvent() {
+      Revoke();
+    }
+
+    NS_INLINE_DECL_REFCOUNTING(nsSynthMouseMoveEvent)
+    
+    void Revoke() {
+      if (mPresShell) {
+        mPresShell->GetPresContext()->RefreshDriver()->
+          RemoveRefreshObserver(this, Flush_Display);
+        mPresShell = nsnull;
+      }
+    }
+    virtual void WillRefresh(mozilla::TimeStamp aTime) {
       if (mPresShell)
         mPresShell->ProcessSynthMouseMoveEvent(mFromScroll);
-      return NS_OK;
     }
   private:
     PresShell* mPresShell;
     bool mFromScroll;
   };
   nsRevocableEventPtr<nsSynthMouseMoveEvent> mSynthMouseMoveEvent;
   void ProcessSynthMouseMoveEvent(bool aFromScroll);