change overlay scrollbar hover show to hover fade in

ui/views/controls/scrollbar/overlay_scroll_bar.cc

 // Copyright 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 "ui/views/controls/scrollbar/overlay_scroll_bar.h"
 
 #include "base/macros.h"
 #include "cc/paint/paint_flags.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/compositor/scoped_layer_animation_settings.h"
@@ skipping 160 matching lines @@
   StartHideCountdown();
 }
 
 void OverlayScrollBar::Show() {
   layer()->SetOpacity(1.0f);
   hide_timer_.Stop();
 }
 
 void OverlayScrollBar::Hide() {
   ui::ScopedLayerAnimationSettings settings(layer()->GetAnimator());
-  settings.SetTransitionDuration(ui::kOverlayScrollbarFadeOutDuration);
+  settings.SetTransitionDuration(ui::kOverlayScrollbarFadeDuration);
   layer()->SetOpacity(0.0f);
 }
 
 void OverlayScrollBar::StartHideCountdown() {
   if (IsMouseHovered())
     return;
   hide_timer_.Start(
-      FROM_HERE, ui::kOverlayScrollbarFadeOutDelay,
+      FROM_HERE, ui::kOverlayScrollbarFadeDelay,
       base::Bind(&OverlayScrollBar::Hide, base::Unretained(this)));
 }
 
 }  // namespace views