[Slimming Paint] Paint the inspector overlay with GraphicsLayer DisplayList.

Source/web/PageOverlayList.h

 /*
  * Copyright (C) 2011 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.
  *
@@ skipping 41 matching lines @@
     // Adds/removes a PageOverlay for given client.
     // Returns true if a PageOverlay is added/removed.
     bool add(WebPageOverlay*, int /* zOrder */);
     bool remove(WebPageOverlay*);
 
     void update();
     void paintWebFrame(GraphicsContext&);
 
     size_t findGraphicsLayer(GraphicsLayer*);
 
+    // FIXME: Really, it should be possible for there to be multiple.
+    // But the signature of WebViewImpl::setOverlayLayer already seems to
+    // preclude that.
+    GraphicsLayer* graphicsLayerForTesting() const;
+
 private:
     typedef Vector<OwnPtr<PageOverlay>, 2> PageOverlays;
 
     explicit PageOverlayList(WebViewImpl*);
 
     // Returns the index of the client found. Otherwise, returns WTF::kNotFound.
     size_t find(WebPageOverlay*);
 
     WebViewImpl* m_viewImpl;
     PageOverlays m_pageOverlays;
 };
 
 } // namespace blink
 
 #endif // PageOverlayList_h