Ensure that scroll position listeners are properly unregistered. b=114221 sr=waterson r=attinasi

git-svn-id: svn://10.0.0.236/trunk@124828 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/layout/generic/nsGfxScrollFrame.cpp

@@ -460,6 +460,10 @@ NS_IMETHODIMP
 nsGfxScrollFrame::Destroy(nsIPresContext* aPresContext)
 
 {
+  nsIScrollableView *view = mInner->GetScrollableView(aPresContext);
+  NS_ASSERTION(view, "unexpected null pointer");
+  if (view)
+    view->RemoveScrollPositionListener(mInner);
   return nsBoxFrame::Destroy(aPresContext);
 }