Recompute slow scroll regions after overflow recalc

Source/core/page/scrolling/ScrollingCoordinator.h

 /*
  * Copyright (C) 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 46 matching lines @@
     ~ScrollingCoordinator();
     DECLARE_TRACE();
 
     void willBeDestroyed();
 
     // Return whether this scrolling coordinator handles scrolling for the given frame view.
     bool coordinatesScrollingForFrameView(FrameView*) const;
 
     // Called when any frame has done its layout.
     void notifyLayoutUpdated();
+    // Called when any frame recalculates its overflows after style change.
+    void notifyOverflowUpdated();
 
     void updateAfterCompositingChangeIfNeeded();
 
     void updateHaveWheelEventHandlers();
     void updateHaveScrollEventHandlers();
 
     // Should be called whenever scrollable area set changes.
     void scrollableAreasDidChange();
 
     // Should be called whenever the slow repaint objects counter changes between zero and one.
@@ skipping 79 matching lines @@
     ScrollbarMap m_verticalScrollbars;
     HashSet<const DeprecatedPaintLayer*> m_layersWithTouchRects;
     bool m_wasFrameScrollable;
 
     MainThreadScrollingReasons m_lastMainThreadScrollingReasons;
 };
 
 } // namespace blink
 
 #endif // ScrollingCoordinator_h