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

Source/core/inspector/InspectorFileSystemAgent.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 473 matching lines @@
     RefPtr<ArrayBuffer> buffer = m_reader->arrayBufferResult();
 
     if (!m_readAsText) {
         String result = base64Encode(static_cast<char*>(buffer->data()), buffer->byteLength());
         reportResult(static_cast<FileError::ErrorCode>(0), &result, 0);
         return;
     }
 
     OwnPtr<TextResourceDecoder> decoder = TextResourceDecoder::create(m_mimeType, m_charset, true);
     String result = decoder->decode(static_cast<char*>(buffer->data()), buffer->byteLength());
-    result.append(decoder->flush());
+    result = result + decoder->flush();
     m_charset = decoder->encoding().name();
     reportResult(static_cast<FileError::ErrorCode>(0), &result, &m_charset);
 }
 
 class DeleteEntryRequest : public RefCounted<DeleteEntryRequest> {
 public:
     static PassRefPtr<DeleteEntryRequest> create(PassRefPtr<DeleteEntryCallback> requestCallback, const KURL& url)
     {
         return adoptRef(new DeleteEntryRequest(requestCallback, url));
     }
@@ skipping 215 matching lines @@
     for (Frame* frame = m_pageAgent->mainFrame(); frame; frame = frame->tree().traverseNext()) {
         if (frame->document() && frame->document()->securityOrigin()->isSameSchemeHostPort(origin))
             return frame->document();
     }
 
     *error = "No frame is available for the request";
     return 0;
 }
 
 } // namespace WebCore