Return transform from transformationForTextBox instead of using out-param

Source/core/rendering/svg/SVGTextLayoutEngine.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010-2012. 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
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 274 matching lines @@
     }
 }
 #endif
 
 void SVGTextLayoutEngine::finalizeTransformMatrices(Vector<SVGInlineTextBox*>& boxes)
 {
     unsigned boxCount = boxes.size();
     if (!boxCount)
         return;
 
-    AffineTransform textBoxTransformation;
     for (unsigned boxPosition = 0; boxPosition < boxCount; ++boxPosition) {
         SVGInlineTextBox* textBox = boxes.at(boxPosition);
-        m_chunkLayoutBuilder.transformationForTextBox(textBox, textBoxTransformation);
+        AffineTransform textBoxTransformation = m_chunkLayoutBuilder.transformationForTextBox(textBox);

[pdr., 2014/07/08 19:00:44]

I think this will create an unnecessary copy. Should we use const
AffineTransform& textBoxTransformation here?

[fs, 2014/07/09 08:53:53]

This should be fine - at least the compiler I used applied RVO here. (There's a
redundant copy emitted for the identity-case transformationForTextBox() though -
fixable, but adds unnecessary contortions IMHO.)

         if (textBoxTransformation.isIdentity())
             continue;
 
         Vector<SVGTextFragment>& fragments = textBox->textFragments();
         unsigned fragmentCount = fragments.size();
         for (unsigned i = 0; i < fragmentCount; ++i) {
             ASSERT(fragments[i].lengthAdjustTransform.isIdentity());
             fragments[i].lengthAdjustTransform = textBoxTransformation;
         }
     }
@@ skipping 336 matching lines @@
     }
 
     if (!didStartTextFragment)
         return;
 
     // Close last open fragment, if needed.
     recordTextFragment(textBox, visualMetricsValues);
 }
 
 }