Get rid of a lot of special code for RenderFlowThread invalidation.

Source/web/LinkHighlight.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 89 matching lines @@
     return m_clipLayer.get();
 }
 
 void LinkHighlight::releaseResources()
 {
     m_node.clear();
 }
 
 void LinkHighlight::attachLinkHighlightToCompositingLayer(const RenderLayerModelObject* paintInvalidationContainer)
 {
-    // FIXME: there should always be a GraphicsLayer. See https://code.google.com/p/chromium/issues/detail?id=359877.
     GraphicsLayer* newGraphicsLayer = paintInvalidationContainer->layer()->graphicsLayerBacking();
-    if (newGraphicsLayer && !newGraphicsLayer->drawsContent())
+    if (!newGraphicsLayer->drawsContent())
         newGraphicsLayer = paintInvalidationContainer->layer()->graphicsLayerBackingForScrolling();
     if (!newGraphicsLayer)
         return;
 
     m_clipLayer->setTransform(SkMatrix44(SkMatrix44::kIdentity_Constructor));
 
     if (m_currentGraphicsLayer != newGraphicsLayer) {
         if (m_currentGraphicsLayer)
             clearGraphicsLayerLinkHighlightPointer();
 
@@ skipping 217 matching lines @@
     // Make sure we update geometry on the next callback from WebViewImpl::layout().
     m_geometryNeedsUpdate = true;
 }
 
 WebLayer* LinkHighlight::layer()
 {
     return clipLayer();
 }
 
 } // namespace blink