Remove the (already disabled) OverflowChangedEvent runtime flag

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
    modify it under the terms of the GNU Library General Public
@@ skipping 611 matching lines @@
     void clearLayoutSubtreeRootsAndMarkContainingBlocks();
 
     // Called when our frame rect changes (or the rect/scroll position of an ancestor changes).
     virtual void frameRectsChanged() override;
 
     friend class LayoutPart;
 
     bool contentsInCompositedLayer() const;
 
     void applyOverflowToViewport(LayoutObject*, ScrollbarMode& hMode, ScrollbarMode& vMode);
-    void updateOverflowStatus(bool horizontalOverflow, bool verticalOverflow);
 
     void updateCounters();
     void forceLayoutParentViewIfNeeded();
     void performPreLayoutTasks();
     void performLayout(bool inSubtreeLayout);
     void scheduleOrPerformPostLayoutTasks();
     void performPostLayoutTasks();
 
     DocumentLifecycle& lifecycle() const;
 
@@ skipping 112 matching lines @@
 
     bool m_firstLayout;
     bool m_isTransparent;
     Color m_baseBackgroundColor;
     IntSize m_lastViewportSize;
     float m_lastZoomFactor;
 
     AtomicString m_mediaType;
     AtomicString m_mediaTypeWhenNotPrinting;
 
-    bool m_overflowStatusDirty;
-    bool m_horizontalOverflow;
-    bool m_verticalOverflow;
-
     // TODO(skobes): Move this to DocumentLoader::InitialScrollState.
     bool m_wasScrolledByUser;
 
     bool m_safeToPropagateScrollToParent;
 
     double m_lastPaintTime;
 
     bool m_isTrackingPaintInvalidations; // Used for testing.
 
     // In frame coordinates.
@@ skipping 91 matching lines @@
     static const unsigned visualPixelThreshold = 32 * 32;
     if (m_visuallyNonEmptyPixelCount > visualPixelThreshold)
         setIsVisuallyNonEmpty();
 }
 
 DEFINE_TYPE_CASTS(FrameView, Widget, widget, widget->isFrameView(), widget.isFrameView());
 
 } // namespace blink
 
 #endif // FrameView_h