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

cc/layers/layer_proto_factory.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_PROTO_FACTORY_H_
+#define CC_LAYERS_LAYER_PROTO_FACTORY_H_
+
+#include "base/macros.h"
+#include "cc/base/cc_export.h"
+#include "cc/layers/layer.h"
+
+namespace cc {
+
+namespace proto {
+class LayerNode;
+}
+
+// A helper class for finding or constructing layers during deserialization.
+class CC_EXPORT LayerProtoFactory {
+ public:
+  // Returns the Layer with proto.id() as the Layer id, if it exists in
+  // |layer_id_map|. Otherwise, a new Layer is constructed of the type given
+  // from proto.type().
+  static scoped_refptr<Layer> FindOrAllocateAndConstruct(
+      const proto::LayerNode& proto,
+      const Layer::LayerIdMap& layer_id_map);
+
+ private:
+  LayerProtoFactory() {}
+  virtual ~LayerProtoFactory() {}
+
+  DISALLOW_COPY_AND_ASSIGN(LayerProtoFactory);
+};
+
+}  // namespace cc
+
+#endif  // CC_LAYERS_LAYER_PROTO_FACTORY_H_