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 177 matching lines @@
     WebDisplayMode displayMode() { return m_displayMode; }
     void setDisplayMode(WebDisplayMode);
 
     // Fixed-position objects.
     typedef HashSet<LayoutObject*> ViewportConstrainedObjectSet;
     void addViewportConstrainedObject(LayoutObject*);
     void removeViewportConstrainedObject(LayoutObject*);
     const ViewportConstrainedObjectSet* viewportConstrainedObjects() const { return m_viewportConstrainedObjects.get(); }
     bool hasViewportConstrainedObjects() const { return m_viewportConstrainedObjects && m_viewportConstrainedObjects->size() > 0; }
 
+    // Sticky objects.
+    void addStickyPositionObject() { ++m_stickyPositionObjectCount; }
+    void removeStickyPositionObject() { --m_stickyPositionObjectCount; }
+    bool hasStickyPositionObjects() const { return m_stickyPositionObjectCount; }
+
     // Objects with background-attachment:fixed.
     void addBackgroundAttachmentFixedObject(LayoutObject*);
     void removeBackgroundAttachmentFixedObject(LayoutObject*);
     bool hasBackgroundAttachmentFixedObjects() const { return m_backgroundAttachmentFixedObjects.size(); }
     void invalidateBackgroundAttachmentFixedObjects();
 
     void handleLoadCompleted();
 
     void updateDocumentAnnotatedRegions() const;
 
@@ skipping 604 matching lines @@
 
     RefPtrWillBeMember<Node> m_scrollAnchor;
 
     // layoutObject to hold our custom scroll corner.
     LayoutScrollbarPart* m_scrollCorner;
 
     OwnPtrWillBeMember<ScrollableAreaSet> m_scrollableAreas;
     OwnPtrWillBeMember<ScrollableAreaSet> m_animatingScrollableAreas;
     OwnPtr<ResizerAreaSet> m_resizerAreas;
     OwnPtr<ViewportConstrainedObjectSet> m_viewportConstrainedObjects;
+    unsigned m_stickyPositionObjectCount;
     ViewportConstrainedObjectSet m_backgroundAttachmentFixedObjects;
     OwnPtrWillBeMember<FrameViewAutoSizeInfo> m_autoSizeInfo;
 
     IntSize m_inputEventsOffsetForEmulation;
     float m_inputEventsScaleFactorForEmulation;
 
     IntSize m_layoutSize;
     bool m_layoutSizeFixedToFrameSize;
 
     Timer<FrameView> m_didScrollTimer;
@@ skipping 87 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