Adapt and reland old position sticky implementation

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
    modify it under the terms of the GNU Library General Public
@@ skipping 651 matching lines @@
     void scheduleUpdateWidgetsIfNecessary();
     void updateWidgetsTimerFired(Timer<FrameView>*);
     bool updateWidgets();
 
     bool processUrlFragmentHelper(const String&, UrlFragmentBehavior);
     void maintainScrollPositionAtAnchor(Node*);
     void scrollToAnchor();
     void scrollPositionChanged();
     void didScrollTimerFired(Timer<FrameView>*);
 
-    void updateLayersAndCompositingAfterScrollIfNeeded();
+    void updateLayersAndCompositingAfterScrollIfNeeded(const DoubleSize& scrollDelta);
 
     static bool computeCompositedSelection(LocalFrame&, CompositedSelection&);
     void updateCompositedSelectionIfNeeded();
 
     // Returns true if the FrameView's own scrollbars overlay its content when visible.
     bool hasOverlayScrollbars() const;
 
     // Returns true if the frame should use custom scrollbars. If true, one of
     // either |customScrollbarElement| or |customScrollbarFrame| will be set to
     // the element or frame which owns the scrollbar with the other set to null.
@@ skipping 177 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