Send takeover msg from MT to CC using the animation path.

cc/layers/layer_impl.h

 // Copyright 2011 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_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 362 matching lines @@
   void set_user_scrollable_horizontal(bool scrollable);
   bool user_scrollable_horizontal() const {
     return user_scrollable_horizontal_;
   }
   void set_user_scrollable_vertical(bool scrollable);
   bool user_scrollable_vertical() const { return user_scrollable_vertical_; }
 
   bool user_scrollable(ScrollbarOrientation orientation) const;
 
   void set_main_thread_scrolling_reasons(
-      uint32_t main_thread_scrolling_reasons);
+      uint32_t main_thread_scrolling_reasons) {
+    main_thread_scrolling_reasons_ = main_thread_scrolling_reasons;
+  }
   uint32_t main_thread_scrolling_reasons() const {
     return main_thread_scrolling_reasons_;
   }
 
   void SetNonFastScrollableRegion(const Region& region) {
     non_fast_scrollable_region_ = region;
   }
   const Region& non_fast_scrollable_region() const {
     return non_fast_scrollable_region_;
   }
@@ skipping 257 matching lines @@
 
   bool scrolls_drawn_descendant_;
   bool has_will_change_transform_hint_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_