Merge 98060 - Hidden composited iframes cause infinite loop

Source/WebCore/rendering/RenderLayer.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 3770 matching lines @@
         m_clipRects = 0;
 #ifndef NDEBUG
         m_clipRectsRoot = 0;
 #endif    
     }
 }
 
 #if USE(ACCELERATED_COMPOSITING)
 RenderLayerBacking* RenderLayer::ensureBacking()
 {
-    if (!m_backing)
+    if (!m_backing) {
         m_backing = adoptPtr(new RenderLayerBacking(this));
+        compositor()->layerBecameComposited(this);
+    }
     return m_backing.get();
 }
 
 void RenderLayer::clearBacking()
 {
+    if (m_backing && !renderer()->documentBeingDestroyed())
+        compositor()->layerBecameNonComposited(this);
     m_backing.clear();
 }
 
 bool RenderLayer::hasCompositedMask() const
 {
     return m_backing && m_backing->hasMaskLayer();
 }
 
 GraphicsLayer* RenderLayer::layerForHorizontalScrollbar() const
 {
@@ skipping 514 matching lines @@
     }
 }
 
 void showLayerTree(const WebCore::RenderObject* renderer)
 {
     if (!renderer)
         return;
     showLayerTree(renderer->enclosingLayer());
 }
 #endif