Add support for (de)serializing cc::Layer hierarchy.

cc/layers/layer_serializer.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 CC_LAYERS_LAYER_SERIALIZER_H_
+#define CC_LAYERS_LAYER_SERIALIZER_H_
+
+#include "base/macros.h"
+#include "cc/base/cc_export.h"
+#include "cc/layers/layer.h"
+
+namespace cc {
+
+namespace proto {
+class LayerNode;
+class LayerUpdate;
+}
+
+// A class to faciliate serialization of a Layer tree.
+class CC_EXPORT LayerSerializer {
+ public:
+  // Starting at |root_layer|, serializes the layer hierarchy into the
+  // proto::LayerNode.
+  static void SerializeLayerHierarchy(const scoped_refptr<Layer> root_layer,
+                                      proto::LayerNode* root_node);
+
+ private:
+  LayerSerializer() {}
+  virtual ~LayerSerializer() {}
+
+  DISALLOW_COPY_AND_ASSIGN(LayerSerializer);
+};
+
+}  // namespace cc
+
+#endif  // CC_LAYERS_LAYER_SERIALIZER_H_