Implement overlay scrollbar fade out for non-composited scrollers.

content/child/webthemeengine_impl_android.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_android.h"
 
 #include "base/logging.h"
 #include "base/sys_info.h"
 #include "skia/ext/platform_canvas.h"
 #include "third_party/WebKit/public/platform/WebRect.h"
@@ skipping 155 matching lines @@
   }
 }
 
 blink::WebSize WebThemeEngineImpl::getSize(WebThemeEngine::Part part) {
   ui::NativeTheme::ExtraParams extra;
   return ui::NativeTheme::GetInstanceForWeb()->GetPartSize(
       NativeThemePart(part), ui::NativeTheme::kNormal, extra);
 }
 
 void WebThemeEngineImpl::getOverlayScrollbarStyle(ScrollbarStyle* style) {
+  // TODO(bokan): Android scrollbars on non-composited scrollers don't
+  // currently fade out so the fadeOutDuration and Delay  Now that this has
+  // been added into Blink for other platforms we should plumb that through for
+  // Android as well.
+  style->fadeOutDelaySeconds = 0;
+  style->fadeOutDurationSeconds = 0;
   if (getMajorVersion() >= kVersionLollipop) {
     style->thumbThickness = 4;
     style->scrollbarMargin = 0;
     style->color = SkColorSetARGB(128, 64, 64, 64);
   } else {
     style->thumbThickness = 3;
     style->scrollbarMargin = 3;
     style->color = SkColorSetARGB(128, 128, 128, 128);
   }
 }
 
 void WebThemeEngineImpl::paint(
     blink::WebCanvas* canvas,
     WebThemeEngine::Part part,
     WebThemeEngine::State state,
     const blink::WebRect& rect,
     const WebThemeEngine::ExtraParams* extra_params) {
   ui::NativeTheme::ExtraParams native_theme_extra_params;
   GetNativeThemeExtraParams(
       part, state, extra_params, &native_theme_extra_params);
   ui::NativeTheme::GetInstanceForWeb()->Paint(
       canvas, NativeThemePart(part), NativeThemeState(state), gfx::Rect(rect),
       native_theme_extra_params);
 }
 }  // namespace content