Implement fade-out animation for Aura overlay scrollbars (CC only).

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 89035df5acb5fefdcaf9ac8ef63e2b78e05c1aca..694605a7b7519bed312c5e83808431e2530406a5 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -1362,17 +1362,19 @@ LayerTreeImpl::CreateScrollbarAnimationController(int scroll_layer_id) {
   DCHECK(!settings().scrollbar_fade_duration.is_zero());
   base::TimeDelta delay = settings().scrollbar_fade_delay;
   base::TimeDelta resize_delay = settings().scrollbar_fade_resize_delay;
-  base::TimeDelta duration = settings().scrollbar_fade_duration;
+  base::TimeDelta fade_duration = settings().scrollbar_fade_duration;
   switch (settings().scrollbar_animator) {
     case LayerTreeSettings::LINEAR_FADE: {
       return ScrollbarAnimationControllerLinearFade::Create(
           scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
-          duration);
+          fade_duration);
     }
     case LayerTreeSettings::THINNING: {
+      base::TimeDelta thinning_duration =
+          settings().scrollbar_thinning_duration;
       return ScrollbarAnimationControllerThinning::Create(
           scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
-          duration);
+          fade_duration, thinning_duration);
     }
     case LayerTreeSettings::NO_ANIMATOR:
       NOTREACHED();