cc: Delay start of scrollbar animation setNeedsRedraw.

cc/layer_tree_host_impl.cc

Index: cc/layer_tree_host_impl.cc
diff --git a/cc/layer_tree_host_impl.cc b/cc/layer_tree_host_impl.cc
index 3c13252533264361d6f3f2234f17bf91f0a72c40..bd3440fb61348ce9daf8579e46170262a0551dab 100644
--- a/cc/layer_tree_host_impl.cc
+++ b/cc/layer_tree_host_impl.cc
@@ -1560,6 +1560,7 @@ void LayerTreeHostImpl::ScrollEnd() {
   if (top_controls_manager_)
     top_controls_manager_->ScrollEnd();
   ClearCurrentlyScrollingLayer();
+  StartScrollbarAnimation(base::TimeTicks::Now());
 }
 
 void LayerTreeHostImpl::PinchGestureBegin() {
@@ -1605,12 +1606,6 @@ void LayerTreeHostImpl::PinchGestureUpdate(float magnify_delta,
 void LayerTreeHostImpl::PinchGestureEnd() {
   pinch_gesture_active_ = false;
 
-  if (RootScrollLayer() &&
-      RootScrollLayer()->scrollbar_animation_controller()) {
-    RootScrollLayer()->scrollbar_animation_controller()->
-        didPinchGestureEnd(base::TimeTicks::Now());
-  }
-
   client_->SetNeedsCommitOnImplThread();
 }
 
@@ -1830,13 +1825,40 @@ void LayerTreeHostImpl::AnimateScrollbarsRecursive(LayerImpl* layer,
 
   ScrollbarAnimationController* scrollbar_controller =
       layer->scrollbar_animation_controller();
-  if (scrollbar_controller && scrollbar_controller->animate(time))
+  if (scrollbar_controller && scrollbar_controller->animate(time)) {
+    TRACE_EVENT_INSTANT0(
+        "cc", "LayerTreeHostImpl::setNeedsRedraw due to AnimateScrollbars");
     client_->SetNeedsRedrawOnImplThread();
+  }
 
   for (size_t i = 0; i < layer->children().size(); ++i)
     AnimateScrollbarsRecursive(layer->children()[i], time);
 }
 
+void LayerTreeHostImpl::StartScrollbarAnimation(base::TimeTicks time) {
+  TRACE_EVENT0("cc", "LayerTreeHostImpl::startScrollbarAnimation");
+  StartScrollbarAnimationRecursive(RootLayer(), time);
+}
+
+void LayerTreeHostImpl::StartScrollbarAnimationRecursive(LayerImpl* layer,
+                                                         base::TimeTicks time) {
+  if (!layer)
+    return;
+
+  ScrollbarAnimationController* scrollbar_controller =
+      layer->scrollbar_animation_controller();
+  if (scrollbar_controller && layer != CurrentlyScrollingLayer()) {
+    double delay = scrollbar_controller->secondsBeforeStart(time);
+    if (delay > 0)
+      client_->RequestScrollbarAnimationOnImplThread(delay);
+    else if (delay == 0 && scrollbar_controller->animate(time))
+      client_->SetNeedsRedrawOnImplThread();
+  }
+
+  for (size_t i = 0; i < layer->children().size(); ++i)
+    StartScrollbarAnimationRecursive(layer->children()[i], time);
+}
+
 void LayerTreeHostImpl::SetTreePriority(TreePriority priority) {
   if (!tile_manager_)
     return;