cc: Delay start of scrollbar animation setNeedsRedraw.

cc/thread_proxy.cc

Index: cc/thread_proxy.cc
diff --git a/cc/thread_proxy.cc b/cc/thread_proxy.cc
index 0d8beb16d81ef13e34f1e1b2d06ed556a8813f87..661ba7756b7b04ee8d0d43b1ab2dcbd79129c7dd 100644
--- a/cc/thread_proxy.cc
+++ b/cc/thread_proxy.cc
@@ -1315,7 +1315,7 @@ void ThreadProxy::RenewTreePriority() {
   Proxy::ImplThread()->PostDelayedTask(
       base::Bind(&ThreadProxy::RenewTreePriorityOnImplThread,
                  weak_factory_on_impl_thread_.GetWeakPtr()),
-      delay.InMilliseconds());
+      delay);
 
   renew_tree_priority_on_impl_thread_pending_ = true;
 }
@@ -1327,4 +1327,15 @@ void ThreadProxy::RenewTreePriorityOnImplThread() {
   RenewTreePriority();
 }
 
+void ThreadProxy::RequestScrollbarAnimationOnImplThread(base::TimeDelta delay) {
+  Proxy::ImplThread()->PostDelayedTask(
+      base::Bind(&ThreadProxy::StartScrollbarAnimationOnImplThread,
+                 impl_thread_weak_ptr_),
+      delay);
+}
+
+void ThreadProxy::StartScrollbarAnimationOnImplThread() {
+  layer_tree_host_impl_->StartScrollbarAnimation(base::TimeTicks::Now());
+}
+
 }  // namespace cc