Aura Overlay Scrollbars appear when mouse hovers over scroller edge

cc/trees/layer_tree_impl.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1377 matching lines @@
 gfx::Size LayerTreeImpl::DrawViewportSize() const {
   return layer_tree_host_impl_->DrawViewportSize();
 }
 
 const gfx::Rect LayerTreeImpl::ViewportRectForTilePriority() const {
   return layer_tree_host_impl_->ViewportRectForTilePriority();
 }
 
 std::unique_ptr<ScrollbarAnimationController>
 LayerTreeImpl::CreateScrollbarAnimationController(int scroll_layer_id) {
-  DCHECK(!settings().scrollbar_fade_delay.is_zero());
-  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 fade_duration = settings().scrollbar_fade_duration;
+  DCHECK(!settings().scrollbar_fade_out_delay.is_zero());
+  DCHECK(!settings().scrollbar_fade_out_duration.is_zero());
+  base::TimeDelta fade_out_delay = settings().scrollbar_fade_out_delay;
+  base::TimeDelta fade_out_resize_delay =
+      settings().scrollbar_fade_out_resize_delay;
+  base::TimeDelta fade_out_duration = settings().scrollbar_fade_out_duration;
   switch (settings().scrollbar_animator) {
     case LayerTreeSettings::ANDROID_OVERLAY: {
       return ScrollbarAnimationController::
           CreateScrollbarAnimationControllerAndroid(
-              scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
-              fade_duration);
+              scroll_layer_id, layer_tree_host_impl_, fade_out_delay,
+              fade_out_resize_delay, fade_out_duration);
     }
     case LayerTreeSettings::AURA_OVERLAY: {
+      DCHECK(!settings().scrollbar_fade_in_delay.is_zero());
+      base::TimeDelta fade_in_delay = settings().scrollbar_fade_in_delay;
       base::TimeDelta thinning_duration =
           settings().scrollbar_thinning_duration;
       return ScrollbarAnimationController::
           CreateScrollbarAnimationControllerAuraOverlay(
-              scroll_layer_id, layer_tree_host_impl_, delay, resize_delay,
-              fade_duration, thinning_duration);
+              scroll_layer_id, layer_tree_host_impl_, fade_in_delay,
+              fade_out_delay, fade_out_resize_delay, fade_out_duration,
+              thinning_duration);
     }
     case LayerTreeSettings::NO_ANIMATOR:
       NOTREACHED();
       break;
   }
   return nullptr;
 }
 
 void LayerTreeImpl::DidAnimateScrollOffset() {
   layer_tree_host_impl_->DidAnimateScrollOffset();
@@ skipping 691 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc