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

Source/core/loader/FormSubmission.cpp

 /*
  * Copyright (C) 2010 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 27 matching lines @@
 #include "core/html/DOMFormData.h"
 #include "core/html/HTMLFormControlElement.h"
 #include "core/html/HTMLFormElement.h"
 #include "core/html/HTMLInputElement.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/loader/FrameLoadRequest.h"
 #include "core/loader/FrameLoader.h"
 #include "platform/network/FormData.h"
 #include "platform/network/FormDataBuilder.h"
 #include "wtf/CurrentTime.h"
+#include "wtf/text/StringBuilder.h"
 #include "wtf/text/TextEncoding.h"
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 static int64_t generateFormDataIdentifier()
 {
     // Initialize to the current time to reduce the likelihood of generating
     // identifiers that overlap with those from past/future browser sessions.
     static int64_t nextIdentifier = static_cast<int64_t>(currentTime() * 1000000.0);
     return ++nextIdentifier;
 }
 
 static void appendMailtoPostFormDataToURL(KURL& url, const FormData& data, const String& encodingType)
 {
     String body = data.flattenToString();
 
     if (equalIgnoringCase(encodingType, "text/plain")) {
         // Convention seems to be to decode, and s/&/\r\n/. Also, spaces are encoded as %20.
         body = decodeURLEscapeSequences(body.replaceWithLiteral('&', "\r\n").replace('+', ' ') + "\r\n");
     }
 
     Vector<char> bodyData;
     bodyData.append("body=", 5);
     FormDataBuilder::encodeStringAsFormData(bodyData, body.utf8());
     body = String(bodyData.data(), bodyData.size()).replaceWithLiteral('+', "%20");
 
-    String query = url.query();
+    StringBuilder query;
+    query.append(url.query());
     if (!query.isEmpty())
         query.append('&');
     query.append(body);
-    url.setQuery(query);
+    url.setQuery(query.toString());
 }
 
 void FormSubmission::Attributes::parseAction(const String& action)
 {
     // FIXME: Can we parse into a KURL?
     m_action = stripLeadingAndTrailingHTMLSpaces(action);
 }
 
 String FormSubmission::Attributes::parseEncodingType(const String& type)
 {
@@ skipping 179 matching lines @@
             frameRequest.resourceRequest().setHTTPContentType(m_contentType);
         else
             frameRequest.resourceRequest().setHTTPContentType(m_contentType + "; boundary=" + m_boundary);
     }
 
     frameRequest.resourceRequest().setURL(requestURL());
     FrameLoader::addHTTPOriginIfNeeded(frameRequest.resourceRequest(), m_origin);
 }
 
 }