Add methods to RenderLayer to get at the painting or scrolling graphics layers, if present.

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 104 matching lines @@
     RenderLayer* renderLayer;
     do {
         renderLayer = renderer->enclosingLayer()->enclosingCompositingLayerForPaintInvalidation();
         if (!renderLayer) {
             renderer = renderer->frame()->ownerRenderer();
             if (!renderer)
                 return 0;
         }
     } while (!renderLayer);
 
-    CompositedLayerMappingPtr compositedLayerMapping = renderLayer->compositingState() == PaintsIntoGroupedBacking ? renderLayer->groupedMapping() : renderLayer->compositedLayerMapping();
-    GraphicsLayer* newGraphicsLayer = renderLayer->compositingState() == PaintsIntoGroupedBacking ? compositedLayerMapping->squashingLayer() : compositedLayerMapping->mainGraphicsLayer();
+    ASSERT(renderLayer->compositingState() != NotComposited);
+
+    GraphicsLayer* newGraphicsLayer = renderLayer->graphicsLayerBacking();
+    if (!newGraphicsLayer->drawsContent()) {
+        newGraphicsLayer = renderLayer->graphicsLayerBackingForScrolling();
+    }
 
     m_clipLayer->setTransform(SkMatrix44(SkMatrix44::kIdentity_Constructor));
 
-    if (!newGraphicsLayer->drawsContent()) {
-        if (renderLayer->scrollableArea() && renderLayer->scrollableArea()->usesCompositedScrolling()) {
-            ASSERT(renderLayer->hasCompositedLayerMapping() && renderLayer->compositedLayerMapping()->scrollingContentsLayer());
-            newGraphicsLayer = compositedLayerMapping->scrollingContentsLayer();
-        }
-    }
-
     if (m_currentGraphicsLayer != newGraphicsLayer) {
         if (m_currentGraphicsLayer)
             clearGraphicsLayerLinkHighlightPointer();
 
         m_currentGraphicsLayer = newGraphicsLayer;
         m_currentGraphicsLayer->addLinkHighlight(this);
     }
 
     return renderLayer;
 }
@@ skipping 207 matching lines @@
     // Make sure we update geometry on the next callback from WebViewImpl::layout().
     m_geometryNeedsUpdate = true;
 }
 
 WebLayer* LinkHighlight::layer()
 {
     return clipLayer();
 }
 
 } // namespace WeKit