cc: Move SyncedScrollOffset to scroll tree

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 "size.proto";
+import "synced_property.proto";
 import "transform.proto";
 import "vector2df.proto";
 
 option optimize_for = LITE_RUNTIME;
 
 package cc.proto;
 
 // The messages declared in this file correspond to the classes declared in
 // cc/trees/property_tree.h
 
@@ skipping 129 matching lines @@
   repeated TreeNode nodes = 2;
   optional bool needs_update = 3;
 
   // The following fields denote the data members for each subclass of
   // PropertyTree. Only one of these fields should be set, depending on the type
   // of this property tree.
   optional TransformTreeData transform_tree_data = 1000;
   optional ScrollTreeData scroll_tree_data = 1001;
 }
 
+message ScrollOffsetMapEntry {
+  required int64 layer_id = 1;
+  optional SyncedProperty scroll_offset = 2;
+}
+
 // Proto for data members of class ScrollTree
 message ScrollTreeData {
   optional int64 currently_scrolling_node_id = 1;
+  repeated ScrollOffsetMapEntry layer_id_to_scroll_offset_map = 2;
 }
 
 // Proto for data members of class TransformTree.
 message TransformTreeData {
   optional bool source_to_parent_updates_allowed = 1;
   optional float page_scale_factor = 2;
   optional float device_scale_factor = 3;
   optional float device_transform_scale_factor = 4;
   repeated int64 nodes_affected_by_inner_viewport_bounds_delta = 7
       [packed = true];
   repeated int64 nodes_affected_by_outer_viewport_bounds_delta = 8
       [packed = true];
 }
 
 // Proto for class PropertyTrees.
-// NEXT ID: 13
+// NEXT ID: 14
 message PropertyTrees {
   optional PropertyTree transform_tree = 1;
   optional PropertyTree effect_tree = 2;
   optional PropertyTree clip_tree = 3;
   optional PropertyTree scroll_tree = 7;
 
   optional bool needs_rebuild = 4;
   optional bool non_root_surfaces_enabled = 5;
   optional bool changed = 11;
   optional bool full_tree_damaged = 12;
   optional int64 sequence_number = 6;
+  optional bool is_main_thread = 13;
+  optional bool is_active = 14;
 
   optional Vector2dF inner_viewport_container_bounds_delta = 8;
   optional Vector2dF outer_viewport_container_bounds_delta = 9;
   optional Vector2dF inner_viewport_scroll_bounds_delta = 10;
 }