Fix computation of local-to-border-box transform for RenderSVGRoot

Source/core/rendering/svg/RenderSVGRoot.cpp

 /*
  * Copyright (C) 2004, 2005, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2007, 2008, 2009 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Google, Inc.
  * Copyright (C) Research In Motion Limited 2011. 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
@@ skipping 319 matching lines @@
 // RenderBox methods will expect coordinates w/o any transforms in coordinates
 // relative to our borderBox origin.  This method gives us exactly that.
 void RenderSVGRoot::buildLocalToBorderBoxTransform()
 {
     SVGSVGElement* svg = toSVGSVGElement(node());
     ASSERT(svg);
     float scale = style()->effectiveZoom();
     FloatPoint translate = svg->currentTranslate();
     LayoutSize borderAndPadding(borderLeft() + paddingLeft(), borderTop() + paddingTop());
     m_localToBorderBoxTransform = svg->viewBoxToViewTransform(contentWidth() / scale, contentHeight() / scale);
-    if (borderAndPadding.isEmpty() && scale == 1 && translate == FloatPoint::zero())
+    if (borderAndPadding.isZero() && scale == 1 && translate == FloatPoint::zero())

[davve, 2014/05/27 09:16:52]

Nit: Would it perhaps be more readable if we instead created the transform and
compared to identity instead?

[fs, 2014/05/27 10:15:31]

Certainly less error-prone at least (slightly more costly, but probably nothing
to worry about in the bigger picture...)

         return;
     m_localToBorderBoxTransform = AffineTransform(scale, 0, 0, scale, borderAndPadding.width() + translate.x(), borderAndPadding.height() + translate.y()) * m_localToBorderBoxTransform;
 }
 
 const AffineTransform& RenderSVGRoot::localToParentTransform() const
 {
     // Slightly optimized version of m_localToParentTransform = AffineTransform::translation(x(), y()) * m_localToBorderBoxTransform;
     m_localToParentTransform = m_localToBorderBoxTransform;
     if (x())
         m_localToParentTransform.setE(m_localToParentTransform.e() + roundToInt(x()));
@@ skipping 106 matching lines @@
             updateHitTestResult(result, pointInBorderBox);
             if (!result.addNodeToRectBasedTestResult(node(), request, locationInContainer, boundsRect))
                 return true;
         }
     }
 
     return false;
 }
 
 }