Adapt and reland old position sticky implementation

third_party/WebKit/Source/core/layout/LayoutInline.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 227 matching lines @@
     void mapRectToPaintInvalidationBacking(const LayoutBoxModelObject* paintInvalidationContainer, LayoutRect&, const PaintInvalidationState*) const final;
 
     // This method differs from clippedOverflowRectForPaintInvalidation in that it includes
     // the rects for culled inline boxes, which aren't necessary for paint invalidation.
     LayoutRect clippedOverflowRect(const LayoutBoxModelObject*, const PaintInvalidationState* = nullptr) const;
 
     void mapLocalToContainer(const LayoutBoxModelObject* paintInvalidationContainer, TransformState&, MapCoordinatesFlags = ApplyContainerFlip, bool* wasFixed = 0, const PaintInvalidationState* = nullptr) const override;
 
     PositionWithAffinity positionForPoint(const LayoutPoint&) final;
 
+    LayoutRect frameRectForStickyPositioning() const override final { return LayoutRect(linesBoundingBox()); }

[chrishtr, 2015/11/04 01:55:18]

Rather than adding a new virtual API method to handle differences between block
and inline layout, I think it would be better
to just do type inspection in LayoutBoxModelObject and call either
linesBoundingBox() or frameRect() as appropriate.

[flackr, 2015/11/25 20:47:53]

Done.

+
     IntRect borderBoundingBox() const final
     {
         IntRect boundingBox = linesBoundingBox();
         return IntRect(0, 0, boundingBox.width(), boundingBox.height());
     }
 
     virtual InlineFlowBox* createInlineFlowBox(); // Subclassed by SVG and Ruby
 
     void dirtyLinesFromChangedChild(LayoutObject* child) final { m_lineBoxes.dirtyLinesFromChangedChild(LineLayoutItem(this), LineLayoutItem(child)); }
 
@@ skipping 16 matching lines @@
 
     LayoutObjectChildList m_children;
     LineBoxList m_lineBoxes; // All of the line boxes created for this inline flow.  For example, <i>Hello<br>world.</i> will have two <i> line boxes.
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutInline, isLayoutInline());
 
 } // namespace blink
 
 #endif // LayoutInline_h