cc: Delay start of scrollbar animation setNeedsRedraw.

cc/layer_tree_impl.h

Index: cc/layer_tree_impl.h
diff --git a/cc/layer_tree_impl.h b/cc/layer_tree_impl.h
index 1b80c2a60c7d70eaa0ef0c35f8a02d06c6c1d4cd..076ee736f38310697170eaf66b59b1e02474eeb1 100644
--- a/cc/layer_tree_impl.h
+++ b/cc/layer_tree_impl.h
@@ -101,10 +101,7 @@ class CC_EXPORT LayerTreeImpl {
   LayerImpl* RootScrollLayer() const;
   LayerImpl* RootClipLayer() const;
   LayerImpl* CurrentlyScrollingLayer() const;
-  void set_currently_scrolling_layer(LayerImpl* layer) {
-    currently_scrolling_layer_ = layer;
-  }
-
+  void SetCurrentlyScrollingLayer(LayerImpl* layer);
   void ClearCurrentlyScrollingLayer();
 
   void FindRootScrollLayer();