Ensure FrameView scrollbars are updated when changing device emulation modes

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

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 406 matching lines @@
           m_overlayScrollbarHorizontal.get());
     if (!m_overlayScrollbarVertical->parent())
       m_innerViewportContainerLayer->addChild(m_overlayScrollbarVertical.get());
   } else {
     m_overlayScrollbarHorizontal->removeFromParent();
     m_overlayScrollbarVertical->removeFromParent();
   }
 
   setupScrollbar(WebScrollbar::Horizontal);
   setupScrollbar(WebScrollbar::Vertical);
+
+  // Ensure existing FrameView scrollbars are removed if the visual viewport
+  // scrollbars are now supplied, or created if the visual viewport no longer
+  // supplies scrollbars.
+  LocalFrame* frame = mainFrame();
+  if (frame && frame->view())
+    frame->view()->visualViewportScrollbarsChanged();
 }
 
 void VisualViewport::setupScrollbar(WebScrollbar::Orientation orientation) {
   bool isHorizontal = orientation == WebScrollbar::Horizontal;
   GraphicsLayer* scrollbarGraphicsLayer =
       isHorizontal ? m_overlayScrollbarHorizontal.get()
                    : m_overlayScrollbarVertical.get();
   std::unique_ptr<WebScrollbarLayer>& webScrollbarLayer =
       isHorizontal ? m_webOverlayScrollbarHorizontal
                    : m_webOverlayScrollbarVertical;
@@ skipping 411 matching lines @@
   } else if (graphicsLayer == m_rootTransformLayer.get()) {
     name = "Root Transform Layer";
   } else {
     ASSERT_NOT_REACHED();
   }
 
   return name;
 }
 
 }  // namespace blink