don't call UpdateView if visibility hasn't changed (bugs 14782, 14925). rev beard/ramiro, appr leaf.

view/src/nsViewManager.cpp

@@ -1921,8 +1921,12 @@ NS_IMETHODIMP nsViewManager :: SetViewClip(nsIView *aView, nsRect *aRect)
 
 NS_IMETHODIMP nsViewManager :: SetViewVisibility(nsIView *aView, nsViewVisibility aVisible)
 {
+  nsViewVisibility isNowVisible;
+  aView->GetVisibility(isNowVisible);
+  if ( aVisible != isNowVisible ) {
     aView->SetVisibility(aVisible);
     UpdateView(aView, nsnull, NS_VMREFRESH_NO_SYNC);
+  }
   return NS_OK;
 }