Inroduce toSVGInlineTextBox, and use it.

Source/core/rendering/svg/RenderSVGInlineText.cpp

 /*
  * Copyright (C) 2006 Oliver Hunt <ojh16@student.canterbury.ac.nz>
  * Copyright (C) 2006 Apple Computer Inc.
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2008 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2010. 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 161 matching lines @@
     float closestDistance = std::numeric_limits<float>::max();
     float closestDistancePosition = 0;
     const SVGTextFragment* closestDistanceFragment = 0;
     SVGInlineTextBox* closestDistanceBox = 0;
 
     AffineTransform fragmentTransform;
     for (InlineTextBox* box = firstTextBox(); box; box = box->nextTextBox()) {
         if (!box->isSVGInlineTextBox())
             continue;
 
-        SVGInlineTextBox* textBox = static_cast<SVGInlineTextBox*>(box);
+        SVGInlineTextBox* textBox = toSVGInlineTextBox(box);
         Vector<SVGTextFragment>& fragments = textBox->textFragments();
 
         unsigned textFragmentsSize = fragments.size();
         for (unsigned i = 0; i < textFragmentsSize; ++i) {
             const SVGTextFragment& fragment = fragments.at(i);
             FloatRect fragmentRect(fragment.x, fragment.y - baseline, fragment.width, fragment.height);
             fragment.buildFragmentTransform(fragmentTransform);
             if (!fragmentTransform.isIdentity())
                 fragmentRect = fragmentTransform.mapRect(fragmentRect);
 
@@ skipping 43 matching lines @@
     FontDescription fontDescription(style->fontDescription());
 
     // FIXME: We need to better handle the case when we compute very small fonts below (below 1pt).
     fontDescription.setComputedSize(FontSize::getComputedSizeFromSpecifiedSize(document, scalingFactor, fontDescription.isAbsoluteSize(), fontDescription.computedSize(), DoNotUseSmartMinimumForFontSize));
 
     scaledFont = Font(fontDescription, 0, 0);
     scaledFont.update(styleResolver->fontSelector());
 }
 
 }