Break two classes defined in json_value_serializer.cc, .h into separate files.

chrome/browser/extensions/external_pref_extension_loader.cc

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/external_pref_extension_loader.h"
 
 #include "base/bind.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
-#include "base/json/json_value_serializer.h"
+#include "base/json/json_file_value_serializer.h"
+#include "base/json/json_string_value_serializer.h"
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/path_service.h"
 #include "chrome/common/chrome_paths.h"
 #include "content/public/browser/browser_thread.h"
 
 using content::BrowserThread;
 
 namespace {
 
@@ skipping 131 matching lines @@
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   prefs_.reset(testing_prefs_->DeepCopy());
   LoadFinished();
 }
 
 ExternalTestingExtensionLoader::~ExternalTestingExtensionLoader() {}
 
 const FilePath ExternalTestingExtensionLoader::GetBaseCrxFilePath() {
   return fake_base_path_;
 }