Remove 'String::append' from some of the blink source.

Source/core/fetch/FontResource.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile, Inc.
  *
  * 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 92 matching lines @@
 }
 
 #if ENABLE(SVG_FONTS)
 bool FontResource::ensureSVGFontData()
 {
     if (!m_externalSVGDocument && !errorOccurred() && !isLoading()) {
         if (m_data) {
             m_externalSVGDocument = SVGDocument::create();
 
             OwnPtr<TextResourceDecoder> decoder = TextResourceDecoder::create("application/xml");
-            String svgSource = decoder->decode(m_data->data(), m_data->size());
+            StringBuilder svgSource;
+            svgSource.append(decoder->decode(m_data->data(), m_data->size()));
             svgSource.append(decoder->flush());
 
-            m_externalSVGDocument->setContent(svgSource);
+            m_externalSVGDocument->setContent(svgSource.toString());
 
             if (decoder->sawError())
                 m_externalSVGDocument = 0;
         }
         if (!m_externalSVGDocument)
             setStatus(DecodeError);
     }
 
     return m_externalSVGDocument;
 }
@@ skipping 35 matching lines @@
 }
 
 void FontResource::checkNotify()
 {
     ResourceClientWalker<FontResourceClient> w(m_clients);
     while (FontResourceClient* c = w.next())
         c->fontLoaded(this);
 }
 
 }