[CSS Shapes] shape-margin in percentage units always computes to 0px

Source/core/rendering/shapes/Shape.h

 /*
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above
  *    copyright notice, this list of conditions and the following
  *    disclaimer.
@@ skipping 43 matching lines @@
 typedef Vector<LineSegment> SegmentList;
 
 
 // A representation of a BasicShape that enables layout code to determine how to break a line up into segments
 // that will fit within or around a shape. The line is defined by a pair of logical Y coordinates and the
 // computed segments are returned as pairs of logical X coordinates. The BasicShape itself is defined in
 // physical coordinates.
 
 class Shape {
 public:
-    static PassOwnPtr<Shape> createShape(const BasicShape*, const LayoutSize& logicalBoxSize, WritingMode, Length margin);
-    static PassOwnPtr<Shape> createRasterShape(Image*, float threshold, const LayoutRect& imageRect, const LayoutRect& marginRect, WritingMode, Length margin);
-    static PassOwnPtr<Shape> createLayoutBoxShape(const RoundedRect&, WritingMode, const Length& margin);
+    static PassOwnPtr<Shape> createShape(const BasicShape*, const LayoutSize& logicalBoxSize, WritingMode, float margin);
+    static PassOwnPtr<Shape> createRasterShape(Image*, float threshold, const LayoutRect& imageRect, const LayoutRect& marginRect, WritingMode, float margin);
+    static PassOwnPtr<Shape> createLayoutBoxShape(const RoundedRect&, WritingMode, float margin);
 
     virtual ~Shape() { }
 
     virtual LayoutRect shapeMarginLogicalBoundingBox() const = 0;
     virtual bool isEmpty() const = 0;
     virtual void getExcludedIntervals(LayoutUnit logicalTop, LayoutUnit logicalHeight, SegmentList&) const = 0;
 
     bool lineOverlapsShapeMarginBounds(LayoutUnit lineTop, LayoutUnit lineHeight) const { return lineOverlapsBoundingBox(lineTop, lineHeight, shapeMarginLogicalBoundingBox()); }
 
 protected:
     float shapeMargin() const { return m_margin; }
 
 private:
     bool lineOverlapsBoundingBox(LayoutUnit lineTop, LayoutUnit lineHeight, const LayoutRect& rect) const
     {
         if (rect.isEmpty())
             return false;
         return (lineTop < rect.maxY() && lineTop + lineHeight > rect.y()) || (!lineHeight && lineTop == rect.y());
     }
 
     WritingMode m_writingMode;
     float m_margin;
 };
 
 } // namespace WebCore
 
 #endif // Shape_h