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

Source/core/inspector/NetworkResourcesData.cpp

 /*
  * Copyright (C) 2011 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:
  *
  * 1. Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *
@@ skipping 113 matching lines @@
         m_dataBuffer = SharedBuffer::create(data, dataLength);
     else
         m_dataBuffer->append(data, dataLength);
 }
 
 size_t NetworkResourcesData::ResourceData::decodeDataToContent()
 {
     ASSERT(!hasContent());
     size_t dataLength = m_dataBuffer->size();
     m_content = m_decoder->decode(m_dataBuffer->data(), m_dataBuffer->size());
-    m_content.append(m_decoder->flush());
+    m_content = m_content + m_decoder->flush();
     m_dataBuffer = nullptr;
     return contentSizeInBytes(m_content) - dataLength;
 }
 
 // NetworkResourcesData
 NetworkResourcesData::NetworkResourcesData()
     : m_contentSize(0)
     , m_maximumResourcesContentSize(maximumResourcesContentSize)
     , m_maximumSingleResourceContentSize(maximumSingleResourceContentSize)
 {
@@ skipping 247 matching lines @@
         String requestId = m_requestIdsDeque.takeFirst();
         ResourceData* resourceData = resourceDataForRequestId(requestId);
         if (resourceData)
             m_contentSize -= resourceData->evictContent();
     }
     return true;
 }
 
 } // namespace WebCore