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

cc/picture_layer_impl.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_IMPL_H_
+#define CC_PICTURE_LAYER_IMPL_H_
+
+#include "cc/layer_impl.h"
+#include "cc/picture.h"
+
+namespace cc {
+
+class CC_EXPORT PictureLayerImpl : public LayerImpl {
+public:
+  static scoped_ptr<PictureLayerImpl> create(int id)
+  {
+      return make_scoped_ptr(new PictureLayerImpl(id));
+  }
+  virtual ~PictureLayerImpl();
+
+protected:
+  PictureLayerImpl(int id);
+
+  Picture picture_;
+
+  friend class PictureLayer;
+  DISALLOW_COPY_AND_ASSIGN(PictureLayerImpl);
+};
+
+}
+
+#endif  // CC_PICTURE_LAYER_IMPL_H_