Implement the framework for the paint property hierarchy

third_party/WebKit/Source/platform/graphics/CompositedDisplayList.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CompositedDisplayList_h
 #define CompositedDisplayList_h
 
 #include "platform/graphics/paint/DisplayItemList.h"
 #include "platform/graphics/paint/DisplayItemTransformTree.h"
 
 namespace blink {
 
 // The result of running the simple layer compositing algorithm. See:
 // https://docs.google.com/document/d/1qF7wpO_lhuxUO6YXKZ3CJuXi0grcb5gKZJBBgnoTd0k/view
+// TODO(pdr): Refactor this into PaintArtifact.
 class CompositedDisplayList {
 public:
     // TODO(pdr): Also add our SimpleLayers here.
     // TODO(pdr): Add the additional property trees (e.g., clip, scroll, etc).
     OwnPtr<const DisplayItemTransformTree> transformTree;
 };
 
 } // namespace blink
 
 #endif // CompositedDisplayList_h