Fix off-by-one error in RasterShape of CSS shapes

Source/core/rendering/shapes/RasterShape.cpp

 /*
  * Copyright (C) 2013 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 133 matching lines @@
     if (y2 < intervals.bounds().y() || y1 >= intervals.bounds().maxY())
         return;
 
     y1 = std::max(y1, intervals.bounds().y());
     y2 = std::min(y2, intervals.bounds().maxY());
     IntShapeInterval excludedInterval;
 
     for (int y = y1; y < y2;  y++)
         excludedInterval.unite(intervals.intervalAt(y));
 
-    result.append(LineSegment(excludedInterval.x1(), excludedInterval.x2() + 1));
+    // Note: |marginIntervals()| returns end-point exclusive
+    // intervals. |excludedInterval.x2()| contains the left-most pixel
+    // offset to the right of the calculated union.
+    result.append(LineSegment(excludedInterval.x1(), excludedInterval.x2()));
 }
 
 } // namespace WebCore