Draw main frame custom scrollbars in root layer scrolling mode.

third_party/WebKit/Source/core/frame/RootFrameViewport.cpp

 // Copyright 2015 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 "core/frame/RootFrameViewport.h"
 
 #include "core/frame/FrameView.h"
 #include "core/layout/ScrollAlignment.h"
 #include "platform/geometry/DoubleRect.h"
 #include "platform/geometry/FloatRect.h"
@@ skipping 284 matching lines @@
 GraphicsLayer* RootFrameViewport::layerForHorizontalScrollbar() const
 {
     return layoutViewport().layerForHorizontalScrollbar();
 }
 
 GraphicsLayer* RootFrameViewport::layerForVerticalScrollbar() const
 {
     return layoutViewport().layerForVerticalScrollbar();
 }
 
+GraphicsLayer* RootFrameViewport::layerForScrollCorner() const
+{
+    return layoutViewport().layerForScrollCorner();
+}
+
 ScrollResult RootFrameViewport::userScroll(ScrollGranularity granularity, const FloatSize& delta)
 {
     // TODO(bokan/ymalik): Once smooth scrolling is permanently enabled we
     // should be able to remove this method override and use the base class
     // version: ScrollableArea::userScroll.
 
     updateScrollAnimator();
 
     // Distribute the scroll between the visual and layout viewport.
 
@@ skipping 103 matching lines @@
 }
 
 DEFINE_TRACE(RootFrameViewport)
 {
     visitor->trace(m_visualViewport);
     visitor->trace(m_layoutViewport);
     ScrollableArea::trace(visitor);
 }
 
 } // namespace blink