Add ScrollTree builder and unit test

cc/trees/property_tree.h

 // Copyright 2014 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_TREES_PROPERTY_TREE_H_
 #define CC_TREES_PROPERTY_TREE_H_
 
 #include <stddef.h>
 
 #include <vector>
@@ skipping 247 matching lines @@
   void FromProtobuf(const proto::TreeNode& proto);
 };
 
 typedef TreeNode<EffectNodeData> EffectNode;
 
 struct CC_EXPORT ScrollNodeData {
   ScrollNodeData();
 
   bool scrollable;
   bool should_scroll_on_main_thread;
-  ScrollBlocksOn scroll_blocks_on;
   bool contains_non_fast_scrollable_region;
 
   int transform_id;
 
   bool operator==(const ScrollNodeData& other) const;
 
   void ToProtobuf(proto::TreeNode* proto) const;
   void FromProtobuf(const proto::TreeNode& proto);
 };
 
@@ skipping 257 matching lines @@
   ClipTree clip_tree;
   ScrollTree scroll_tree;
   bool needs_rebuild;
   bool non_root_surfaces_enabled;
   int sequence_number;
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_PROPERTY_TREE_H_