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

cc/layers/layer.h

 // Copyright 2010 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_H_
 #define CC_LAYERS_LAYER_H_
 
 #include <set>
 #include <string>
 #include <vector>
@@ skipping 49 matching lines @@
 class LayerTreeHost;
 class LayerTreeHostCommon;
 class LayerTreeImpl;
 class LayerTreeSettings;
 class RenderingStatsInstrumentation;
 class ResourceUpdateQueue;
 class ScrollbarLayerInterface;
 class SimpleEnclosedRegion;
 struct AnimationEvent;
 
+namespace proto {
+class LayerNode;
+}  // proto
+
 // Base class for composited layers. Special layer types are derived from
 // this class.
 class CC_EXPORT Layer : public base::RefCounted<Layer>,
                         public LayerAnimationValueObserver,
                         public LayerAnimationValueProvider {
  public:
   typedef LayerList LayerListType;
+  typedef base::hash_map<int, scoped_refptr<Layer>> LayerIdMap;
 
   enum LayerIdLabels {
     INVALID_ID = -1,
   };
 
   static scoped_refptr<Layer> Create(const LayerSettings& settings);
 
   int id() const { return layer_id_; }
 
   Layer* RootLayer();
@@ skipping 264 matching lines @@
   virtual void SetIsMask(bool is_mask) {}
   virtual bool IsSuitableForGpuRasterization() const;
 
   virtual scoped_refptr<base::trace_event::ConvertableToTraceFormat>
   TakeDebugInfo();
 
   void SetLayerClient(LayerClient* client) { client_ = client; }
 
   virtual void PushPropertiesTo(LayerImpl* layer);
 
+  // Recursively iterate over this layer and all children and write the
+  // hierarchical structure to the given LayerNode proto. In addition to the
+  // structure itself, the Layer id and type is also written to facilitate
+  // construction of the correct layer on the client.
+  virtual void ToLayerNodeProto(proto::LayerNode* proto) const;
+  // Recursively iterate over the given LayerNode proto and read the structure

[vmpstr, 2015/10/23 21:26:10]

nit: can you put a blank line before this one?

[nyquist, 2015/10/26 03:14:29]

Done.

+  // into this node and its children. The |layer_map| should be used to look
+  // for previously existing Layers, since they should be re-used between each
+  // hierarchy update.
+  virtual void FromLayerNodeProto(const proto::LayerNode& proto,
+                                  const LayerIdMap& layer_map);
+
   LayerTreeHost* layer_tree_host() { return layer_tree_host_; }
   const LayerTreeHost* layer_tree_host() const { return layer_tree_host_; }
 
   bool AddAnimation(scoped_ptr<Animation> animation);
   void PauseAnimation(int animation_id, double time_offset);
   void RemoveAnimation(int animation_id);
   void RemoveAnimation(int animation_id, Animation::TargetProperty property);
   LayerAnimationController* layer_animation_controller() const {
     return layer_animation_controller_.get();
   }
@@ skipping 342 matching lines @@
 
   std::vector<FrameTimingRequest> frame_timing_requests_;
   bool frame_timing_requests_dirty_;
 
   DISALLOW_COPY_AND_ASSIGN(Layer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_H_