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

chrome/test/automation/automation_proxy_uitest.cc

 // 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 <string>
 
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/i18n/rtl.h"
-#include "base/json/json_value_serializer.h"
+#include "base/json/json_string_value_serializer.h"
 #include "base/md5.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/scoped_temp_dir.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
 #include "base/sys_info.h"
 #include "base/test/test_timeouts.h"
 #include "base/utf_string_conversions.h"
 #include "build/build_config.h"
 #include "chrome/app/chrome_command_ids.h"
@@ skipping 1558 matching lines @@
 
   std::string data;
   ASSERT_NO_FATAL_FAILURE(AssertReadPNG(snapshot_path_, &data));
   EXPECT_STREQ(kReferenceMd5, base::MD5String(data).c_str());
   if (CommandLine::ForCurrentProcess()->HasSwitch("dump-test-image")) {
     FilePath path(FILE_PATH_LITERAL("snapshot.png"));
     EXPECT_EQ(file_util::WriteFile(path, &data[0], data.length()),
               static_cast<int>(data.length()));
   }
 }