Fix getBBox() returning (0,0) bug when width or height is zero

Source/core/rendering/svg/RenderSVGEllipse.cpp

 /*
  * Copyright (C) 2012 Google, Inc.
  * 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.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 45 matching lines @@
     // Fallback to RenderSVGShape if shape has a non-scaling stroke.
     if (hasNonScalingStroke()) {
         RenderSVGShape::updateShapeFromElement();
         m_usePathFallback = true;
         return;
     } else
         m_usePathFallback = false;
 
     calculateRadiiAndCenter();
 
-    // Spec: "A value of zero disables rendering of the element."
-    if (m_radii.width() <= 0 || m_radii.height() <= 0)
+    // Spec: "A negative value is an error. A value of zero disables rendering of the element."
+    if (m_radii.isZero() || m_radii.width() < 0 || m_radii.height() < 0)
         return;
 
     m_fillBoundingBox = FloatRect(m_center.x() - m_radii.width(), m_center.y() - m_radii.height(), 2 * m_radii.width(), 2 * m_radii.height());
     m_strokeBoundingBox = m_fillBoundingBox;
     if (style()->svgStyle()->hasStroke())
         m_strokeBoundingBox.inflate(strokeWidth() / 2);
 }
 
 void RenderSVGEllipse::calculateRadiiAndCenter()
 {
@@ skipping 68 matching lines @@
     FloatPoint center = FloatPoint(m_center.x() - point.x(), m_center.y() - point.y());
 
     // This works by checking if the point satisfies the ellipse equation.
     // (x/rX)^2 + (y/rY)^2 <= 1
     float xrX = center.x() / m_radii.width();
     float yrY = center.y() / m_radii.height();
     return xrX * xrX + yrY * yrY <= 1.0;
 }
 
 }