Direct composite canvas background if possible.

Source/core/testing/Internals.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  * Copyright (C) 2013 Apple 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.
@@ skipping 1582 matching lines @@
 
     element->document()->updateLayout();
 
     RenderObject* renderer = element->renderer();
     if (!renderer || !renderer->isBox()) {
         ec = InvalidAccessError;
         return String();
     }
 
     RenderLayer* layer = toRenderBox(renderer)->layer();
-    if (!layer) {
-        ec = InvalidAccessError;
-        return String();
-    }
-
-    if (!layer->backing() || !layer->backing()->graphicsLayer()) {
+    if (!layer
+        || !layer->backing()
+        || !layer->backing()->graphicsLayer()) {
         // Don't raise exception in these cases which may be normally used in tests.
         return String();
     }
 
     return layer->backing()->graphicsLayer()->layerTreeAsText(flags);
 }
 
 void Internals::setNeedsCompositedScrolling(Element* element, unsigned needsCompositedScrolling, ExceptionCode& ec)
 {
     if (!element) {
@@ skipping 430 matching lines @@
 
     RenderObject* renderer = select->renderer();
     if (!renderer->isMenuList())
         return false;
 
     RenderMenuList* menuList = toRenderMenuList(renderer);
     return menuList->popupIsVisible();
 }
 
 }