Disentangle updating the ScrollingCoordinator from RenderLayerCompositor

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 2814 matching lines @@
 
 void FrameView::updateLayoutAndStyleForPainting()
 {
     // Updating layout can run script, which can tear down the FrameView.
     RefPtr<FrameView> protector(this);
 
     updateLayoutAndStyleIfNeededRecursive();
 
     if (RenderView* view = renderView()) {
         InspectorInstrumentation::willUpdateLayerTree(view->frame());
+
         view->compositor()->updateIfNeededRecursive();
+
+        if (view->compositor()->inCompositingMode() && m_frame->isMainFrame())
+            m_frame->page()->scrollingCoordinator()->updateAfterCompositingChangeIfNeeded();
+
         InspectorInstrumentation::didUpdateLayerTree(view->frame());
     }
 
     scrollContentsIfNeededRecursive();
 }
 
 void FrameView::updateLayoutAndStyleIfNeededRecursive()
 {
     // We have to crawl our entire tree looking for any FrameViews that need
     // layout and make sure they are up to date.
@@ skipping 427 matching lines @@
 void FrameView::willRemoveScrollbar(Scrollbar* scrollbar, ScrollbarOrientation orientation)
 {
     ScrollableArea::willRemoveScrollbar(scrollbar, orientation);
     if (AXObjectCache* cache = axObjectCache()) {
         cache->remove(scrollbar);
         cache->handleScrollbarUpdate(this);
     }
 }
 
 } // namespace WebCore