cc:: Add transform nodes at boundaries of 3d rendering contexts

cc/proto/property_tree.proto

 // 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.
 
 syntax = "proto2";
 
 import "rectf.proto";
 import "scroll_offset.proto";
 import "transform.proto";
 import "vector2df.proto";
@@ skipping 40 matching lines @@
   optional float local_maximum_animation_target_scale = 30;
   optional float local_starting_animation_scale = 31;
   optional float combined_maximum_animation_target_scale = 32;
   optional float combined_starting_animation_scale = 33;
 
   optional Vector2dF sublayer_scale = 34;
   optional ScrollOffset scroll_offset = 35;
   optional Vector2dF scroll_snap = 36;
   optional Vector2dF source_offset = 37;
   optional Vector2dF source_to_parent = 38;
+  optional int64 sorting_context_id = 39;
 }
 
 // Proto for struct ClipNodeData.
 message ClipNodeData {
   optional RectF clip = 1;
   optional RectF combined_clip_in_target_space = 2;
   optional RectF clip_in_target_space = 3;
 
   optional int64 transform_id = 4;
   optional int64 target_id = 5;
@@ skipping 84 matching lines @@
 message PropertyTrees {
   optional PropertyTree transform_tree = 1;
   optional PropertyTree effect_tree = 2;
   optional PropertyTree clip_tree = 3;
   optional PropertyTree scroll_tree = 4;
 
   optional bool needs_rebuild = 5;
   optional bool non_root_surfaces_enabled = 6;
   optional int64 sequence_number = 7;
 }