change overlay scrollbar hover show to hover fade in

cc/layers/scrollbar_layer_unittest.cc

 // Copyright 2012 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 <stddef.h>
 
 #include <unordered_map>
 
 #include "base/memory/ptr_util.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 92 matching lines @@
  public:
   ScrollbarLayerTest() {
     layer_tree_settings_.single_thread_proxy_scheduler = false;
     layer_tree_settings_.use_zero_copy = true;
     layer_tree_settings_.scrollbar_animator =
         LayerTreeSettings::ANDROID_OVERLAY;
     layer_tree_settings_.scrollbar_show_delay =
         base::TimeDelta::FromMilliseconds(20);
     layer_tree_settings_.scrollbar_fade_out_delay =
         base::TimeDelta::FromMilliseconds(20);
+    layer_tree_settings_.scrollbar_fade_in_duration =
+        base::TimeDelta::FromMilliseconds(20);
     layer_tree_settings_.scrollbar_fade_out_duration =
         base::TimeDelta::FromMilliseconds(20);
 
     scrollbar_layer_id_ = -1;
 
     animation_host_ = AnimationHost::CreateForTesting(ThreadInstance::MAIN);
 
     LayerTreeHost::InitParams params;
     params.client = &fake_client_;
     params.settings = &layer_tree_settings_;
@@ skipping 1112 matching lines @@
   TestScale(gfx::Rect(1240, 0, 15, 1333), 2.7754839f);
   TestScale(gfx::Rect(1240, 0, 15, 677), 2.46677136f);
 
   // Horizontal Scrollbars.
   TestScale(gfx::Rect(0, 1240, 1333, 15), 2.7754839f);
   TestScale(gfx::Rect(0, 1240, 677, 15), 2.46677136f);
 }
 
 }  // namespace
 }  // namespace cc