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

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index e437904b61209cf72d07a02e3e0a5a66cd806d07..f0b482cc5cbffdb7754d55fbeabb356bb809b6a4 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -380,7 +380,9 @@ class CC_EXPORT LayerImpl {
   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_;
   }