change overlay scrollbar hover show to hover fade in

content/child/webthemeengine_impl_default.cc

 // Copyright 2014 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/child/webthemeengine_impl_default.h"
 
 #include "build/build_config.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/WebKit/public/platform/WebRect.h"
 #include "third_party/WebKit/public/platform/WebSize.h"
@@ skipping 230 matching lines @@
       part, state, extra_params, &native_theme_extra_params);
   ui::NativeTheme::GetInstanceForWeb()->Paint(
       canvas, NativeThemePart(part), NativeThemeState(state), gfx::Rect(rect),
       native_theme_extra_params);
 }
 
 void WebThemeEngineImpl::GetOverlayScrollbarStyle(ScrollbarStyle* style) {
   style->fade_out_delay_seconds =
       ui::kOverlayScrollbarFadeOutDelay.InSecondsF();
   style->fade_out_duration_seconds =
-      ui::kOverlayScrollbarFadeOutDuration.InSecondsF();
+      ui::kOverlayScrollbarFadeDuration.InSecondsF();
   // The other fields in this struct are used only on Android to draw solid
   // color scrollbars. On other platforms the scrollbars are painted in
   // NativeTheme so these fields are unused.
 }
 
 bool WebThemeEngineImpl::SupportsNinePatch(Part part) const {
   return ui::NativeTheme::GetInstanceForWeb()->SupportsNinePatch(
       NativeThemePart(part));
 }
 
@@ skipping 15 matching lines @@
     int32_t vertical_arrow_bitmap_height,
     int32_t horizontal_arrow_bitmap_width) {
   g_vertical_scroll_bar_width = vertical_scroll_bar_width;
   g_horizontal_scroll_bar_height = horizontal_scroll_bar_height;
   g_vertical_arrow_bitmap_height = vertical_arrow_bitmap_height;
   g_horizontal_arrow_bitmap_width = horizontal_arrow_bitmap_width;
 }
 #endif
 
 }  // namespace content