Added serialization to protobufs for property trees.

cc/trees/property_tree.h

Index: cc/trees/property_tree.h
diff --git a/cc/trees/property_tree.h b/cc/trees/property_tree.h
index 6f26ef68768c594a9ce8a86c524b0ea374a50799..94e87d0abec9d00436ce98fc35dcd3e8248e937c 100644
--- a/cc/trees/property_tree.h
+++ b/cc/trees/property_tree.h
@@ -15,6 +15,22 @@
 
 namespace cc {
 
+namespace proto {
+class ClipNodeData;
+class EffectNodeData;
+class PropertyTree;
+class PropertyTrees;
+class TranformNodeData;
+class TransformTreeData;
+class TreeNode;
+}
+
+// Each class declared here has a corresponding proto defined in
+// cc/proto/property_tree.proto. When making any changes to a class structure
+// including addition/deletion/updation of a field, please also make the
+// change to its proto and the ToProtobuf and FromProtobuf methods for that
+// class.
+
 template <typename T>
 struct CC_EXPORT TreeNode {
   TreeNode() : id(-1), parent_id(-1), owner_id(-1), data() {}
@@ -22,6 +38,9 @@ struct CC_EXPORT TreeNode {
   int parent_id;
   int owner_id;
   T data;
+
+  void ToProtobuf(proto::TreeNode* proto) const;
+  void FromProtobuf(const proto::TreeNode& proto);
 };
 
 struct CC_EXPORT TransformNodeData {
@@ -150,6 +169,9 @@ struct CC_EXPORT TransformNodeData {
 
   void update_post_local_transform(const gfx::PointF& position,
                                    const gfx::Point3F& transform_origin);
+
+  void ToProtobuf(proto::TreeNode* proto) const;
+  void FromProtobuf(const proto::TreeNode& proto);
 };
 
 typedef TreeNode<TransformNodeData> TransformNode;
@@ -198,6 +220,11 @@ struct CC_EXPORT ClipNodeData {
 
   // Nodes that correspond to unclipped surfaces disregard ancestor clips.
   bool resets_clip : 1;
+
+  bool operator==(const ClipNodeData& other) const;
+
+  void ToProtobuf(proto::TreeNode* proto) const;
+  void FromProtobuf(const proto::TreeNode& proto);
 };
 
 typedef TreeNode<ClipNodeData> ClipNode;
@@ -211,6 +238,11 @@ struct CC_EXPORT EffectNodeData {
   bool has_render_surface;
   int transform_id;
   int clip_id;
+
+  bool operator==(const EffectNodeData& other) const;
+
+  void ToProtobuf(proto::TreeNode* proto) const;
+  void FromProtobuf(const proto::TreeNode& proto);
 };
 
 typedef TreeNode<EffectNodeData> EffectNode;
@@ -250,6 +282,9 @@ class CC_EXPORT PropertyTree {
 
   int next_available_id() const { return static_cast<int>(size()); }
 
+  void ToProtobuf(proto::PropertyTree* proto) const;
+  void FromProtobuf(const proto::PropertyTree& proto);
+
  private:
   // Copy and assign are permitted. This is how we do tree sync.
   std::vector<T> nodes_;
@@ -348,6 +383,9 @@ class CC_EXPORT TransformTree final : public PropertyTree<TransformNode> {
   bool HasNodesAffectedByInnerViewportBoundsDelta() const;
   bool HasNodesAffectedByOuterViewportBoundsDelta() const;
 
+  void ToProtobuf(proto::PropertyTree* proto) const;
+  void FromProtobuf(const proto::PropertyTree& proto);
+
  private:
   // Returns true iff the node at |desc_id| is a descendant of the node at
   // |anc_id|.
@@ -400,17 +438,26 @@ class CC_EXPORT ClipTree final : public PropertyTree<ClipNode> {
  public:
   void SetViewportClip(gfx::RectF viewport_rect);
   gfx::RectF ViewportClip();
+
+  void ToProtobuf(proto::PropertyTree* proto) const;
+  void FromProtobuf(const proto::PropertyTree& proto);
 };
 
 class CC_EXPORT EffectTree final : public PropertyTree<EffectNode> {
  public:
   void UpdateOpacities(int id);
+
+  void ToProtobuf(proto::PropertyTree* proto) const;
+  void FromProtobuf(const proto::PropertyTree& proto);
 };
 
 class CC_EXPORT PropertyTrees final {
  public:
   PropertyTrees();
 
+  static PropertyTrees CreateFromProtobuf(const proto::PropertyTrees& proto);

[David Trainor- moved to gerrit, 2015/11/12 22:46:11]

do we want to just return a PropertyTrees object here?  What's the overhead of
doing this?  I don't know enough about whether or not the compiler can be smart
in these cases.

[Khushal, 2015/11/13 10:33:13]

Yeah, just returning property trees is bad. I added it as a method to property
trees. This way when we de-serialize the layer tree host for a commit, we can
just de-serialize into the property trees in the LTH.

+  void ToProtobuf(proto::PropertyTrees* proto) const;
+
   TransformTree transform_tree;
   EffectTree effect_tree;
   ClipTree clip_tree;