cc: Add some impl-side painting stub classes and APIs

cc/picture_layer.h

+// Copyright 2012 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 CC_PICTURE_LAYER_H_
+#define CC_PICTURE_LAYER_H_
+
+#include "cc/layer.h"
+#include "cc/picture.h"
+
+namespace cc {
+
+class ContentLayerClient;
+
+class CC_EXPORT PictureLayer : public Layer {
+public:
+  static scoped_refptr<PictureLayer> create(ContentLayerClient*);
+
+  void clearClient() { client_ = 0; }
+
+  // Implement Layer interface
+  virtual bool drawsContent() const OVERRIDE;
+  virtual scoped_ptr<LayerImpl> createLayerImpl() OVERRIDE;
+  virtual void pushPropertiesTo(LayerImpl*) OVERRIDE;
+
+protected:
+  explicit PictureLayer(ContentLayerClient*);
+  virtual ~PictureLayer();
+
+private:
+  ContentLayerClient* client_;
+  Picture picture_;
+};
+
+}  // namespace cc
+
+#endif  // CC_PICTURE_LAYER_H_