Ensure FrameView scrollbars are updated when changing device emulation modes

third_party/WebKit/Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
    reserved.
 
    This library is free software; you can redistribute it and/or
@@ skipping 813 matching lines @@
   // https://crbug.com/680606. Animation timelines and hosts for scrolling
   // are normally owned by ScrollingCoordinator, but there is only one
   // of those objects per page. To get around this, we temporarily stash a
   // unique timeline and host on each OOPIF FrameView.
   void setAnimationTimeline(std::unique_ptr<CompositorAnimationTimeline>);
   void setAnimationHost(std::unique_ptr<CompositorAnimationHost>);
 
   // Returns the GeometryMapper associated with the root local frame.
   GeometryMapper& geometryMapper();
 
+  // The visual viewport can supply scrollbars which affect the existence of
+  // our scrollbars (see: computeScrollbarExistence).
+  void visualViewportScrollbarsChanged();
+
  protected:
   // Scroll the content via the compositor.
   bool scrollContentsFastPath(const IntSize& scrollDelta);
 
   // Scroll the content by invalidating everything.
   void scrollContentsSlowPath();
 
   ScrollBehavior scrollBehaviorStyle() const override;
 
   void scrollContentsIfNeeded();
@@ skipping 355 matching lines @@
   // main thread scrolling reasons.
   Vector<int> m_mainThreadScrollingReasonsCounter;
 
   // TODO(kenrb): Remove these when https://crbug.com/680606 is resolved.
   std::unique_ptr<CompositorAnimationTimeline> m_animationTimeline;
   std::unique_ptr<CompositorAnimationHost> m_animationHost;
 
   std::unique_ptr<GeometryMapper> m_geometryMapper;
 
   Member<PrintContext> m_printContext;
+
+  FRIEND_TEST_ALL_PREFIXES(WebViewTest, DeviceEmulationResetScrollbars);
 };
 
 inline void FrameView::incrementVisuallyNonEmptyCharacterCount(unsigned count) {
   if (m_isVisuallyNonEmpty)
     return;
   m_visuallyNonEmptyCharacterCount += count;
   // Use a threshold value to prevent very small amounts of visible content from
   // triggering didMeaningfulLayout.  The first few hundred characters rarely
   // contain the interesting content of the page.
   static const unsigned visualCharacterThreshold = 200;
@@ skipping 20 matching lines @@
                   widget.isFrameView());
 DEFINE_TYPE_CASTS(FrameView,
                   ScrollableArea,
                   scrollableArea,
                   scrollableArea->isFrameView(),
                   scrollableArea.isFrameView());
 
 }  // namespace blink
 
 #endif  // FrameView_h