change overlay scrollbar hover show to hover fade in

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 2013 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 "content/renderer/gpu/render_widget_compositor.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 429 matching lines @@
   // TODO(danakj): Only do this on low end devices.
   settings.create_low_res_tiling = true;
 #else  // defined(OS_ANDROID)
 #if !defined(OS_MACOSX)
   if (ui::IsOverlayScrollbarEnabled()) {
     settings.scrollbar_animator = cc::LayerTreeSettings::AURA_OVERLAY;
     settings.scrollbar_show_delay = ui::kOverlayScrollbarShowDelay;
     settings.scrollbar_fade_out_delay = ui::kOverlayScrollbarFadeOutDelay;
     settings.scrollbar_fade_out_resize_delay =
         ui::kOverlayScrollbarFadeOutDelay;
+    settings.scrollbar_fade_in_duration = ui::kOverlayScrollbarFadeInDuration;
     settings.scrollbar_fade_out_duration = ui::kOverlayScrollbarFadeOutDuration;
     settings.scrollbar_thinning_duration =
         ui::kOverlayScrollbarThinningDuration;
   } else {
     // TODO(bokan): This section is probably unneeded? We don't use scrollbar
     // animations for non overlay scrollbars.
     settings.scrollbar_animator = cc::LayerTreeSettings::ANDROID_OVERLAY;
     settings.solid_color_scrollbar_color = SkColorSetARGB(128, 128, 128, 128);
     settings.scrollbar_fade_out_delay = base::TimeDelta::FromMilliseconds(500);
     settings.scrollbar_fade_out_resize_delay =
@@ skipping 687 matching lines @@
 void RenderWidgetCompositor::SetContentSourceId(uint32_t id) {
   layer_tree_host_->SetContentSourceId(id);
 }
 
 void RenderWidgetCompositor::SetLocalSurfaceId(
     const cc::LocalSurfaceId& local_surface_id) {
   layer_tree_host_->SetLocalSurfaceId(local_surface_id);
 }
 
 }  // namespace content