One more instance of StringBuilder::Append replacing String::Append.

Source/core/dom/CharacterData.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. 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.
  *
@@ skipping 52 matching lines @@
         exceptionState.throwDOMException(IndexSizeError, "The offset " + String::number(offset) + " is greater than the node's length (" + String::number(length()) + ").");
         return String();
     }
 
     return m_data.substring(offset, count);
 }
 
 void CharacterData::parserAppendData(const String& string)
 {
     unsigned oldLength = m_data.length();
-    m_data.append(string);
+    m_data = m_data + string;
 
     ASSERT(!renderer() || isTextNode());
     if (isTextNode())
         toText(this)->updateTextRenderer(oldLength, 0);
 
     document().incDOMTreeVersion();
 
     if (parentNode())
         parentNode()->childrenChanged();
 }
@@ skipping 121 matching lines @@
 {
     return static_cast<int>(length());
 }
 
 bool CharacterData::offsetInCharacters() const
 {
     return true;
 }
 
 } // namespace WebCore