position:sticky should stick for the enclosing overflow ancestor

Source/core/rendering/RenderBoxModelObject.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 48 matching lines @@
 // at http://www.w3.org/TR/CSS21/box.html
 
 class RenderBoxModelObject : public RenderLayerModelObject {
 public:
     RenderBoxModelObject(ContainerNode*);
     virtual ~RenderBoxModelObject();
 
     LayoutSize relativePositionOffset() const;
     LayoutSize relativePositionLogicalOffset() const { return style()->isHorizontalWritingMode() ? relativePositionOffset() : relativePositionOffset().transposedSize(); }
 
-    void computeStickyPositionConstraints(StickyPositionViewportConstraints&, const FloatRect& viewportRect) const;
+    void computeStickyPositionConstraints(StickyPositionViewportConstraints&, const FloatRect& constrainingRect) const;
     LayoutSize stickyPositionOffset() const;
     LayoutSize stickyPositionLogicalOffset() const { return style()->isHorizontalWritingMode() ? stickyPositionOffset() : stickyPositionOffset().transposedSize(); }
 
     LayoutSize offsetForInFlowPosition() const;
 
     // IE extensions. Used to calculate offsetWidth/Height.  Overridden by inlines (RenderFlow)
     // to return the remaining width on a given line (and the height of a single line).
     virtual LayoutUnit offsetLeft() const;
     virtual LayoutUnit offsetTop() const;
     virtual LayoutUnit offsetWidth() const = 0;
@@ skipping 249 matching lines @@
     void drawBoxSideFromPath(GraphicsContext*, const LayoutRect&, const Path&, const class BorderEdge[],
                             float thickness, float drawThickness, BoxSide, const RenderStyle*,
                             Color, EBorderStyle, BackgroundBleedAvoidance, bool includeLogicalLeftEdge, bool includeLogicalRightEdge);
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderBoxModelObject, isBoxModelObject());
 
 } // namespace WebCore
 
 #endif // RenderBoxModelObject_h