Fix scrollbar buttons on ChromeOS.

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 153 matching lines @@
       break;  // Parts that have no extra params get here.
   }
 }
 
 blink::WebSize WebThemeEngineImpl::getSize(WebThemeEngine::Part part) {
   ui::NativeTheme::ExtraParams extra;
   return ui::NativeTheme::GetInstanceForWeb()->GetPartSize(
       NativeThemePart(part), ui::NativeTheme::kNormal, extra);
 }
 
+bool WebThemeEngineImpl::hasScrollbarButtons() {
+  return ui::NativeTheme::GetInstanceForWeb()->HasScrollbarButtons();
+}
+
 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);
 }
 
 void WebThemeEngineImpl::paintStateTransition(blink::WebCanvas* canvas,
                                               WebThemeEngine::Part part,
                                               WebThemeEngine::State startState,
                                               WebThemeEngine::State endState,
                                               double progress,
                                               const blink::WebRect& rect) {
   ui::NativeTheme::GetInstanceForWeb()->PaintStateTransition(
       canvas, NativeThemePart(part), NativeThemeState(startState),
       NativeThemeState(endState), progress, gfx::Rect(rect));
 }
 
 }  // namespace content