Move ReadFileToString to the base namespace.

chrome/browser/ui/cocoa/extensions/extension_install_prompt_test_utils.mm

 // 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.
 
 #import "chrome/browser/ui/cocoa/extensions/extension_install_prompt_test_utils.h"
 
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/json/json_file_value_serializer.h"
 #include "base/path_service.h"
@@ skipping 40 matching lines @@
 }
 
 gfx::Image LoadInstallPromptIcon() {
   base::FilePath path;
   PathService::Get(chrome::DIR_TEST_DATA, &path);
   path = path.AppendASCII("extensions")
              .AppendASCII("install_prompt")
              .AppendASCII("icon.png");
 
   std::string file_contents;
-  file_util::ReadFileToString(path, &file_contents);
+  base::ReadFileToString(path, &file_contents);
 
   return gfx::Image::CreateFrom1xPNGBytes(
       reinterpret_cast<const unsigned char*>(file_contents.c_str()),
       file_contents.length());
 }
 
 ExtensionInstallPrompt::Prompt BuildExtensionInstallPrompt(
     Extension* extension) {
   ExtensionInstallPrompt::Prompt prompt(ExtensionInstallPrompt::INSTALL_PROMPT);
   prompt.set_extension(extension);
   prompt.set_icon(LoadInstallPromptIcon());
   return prompt;
 }
 
 ExtensionInstallPrompt::Prompt BuildExtensionPostInstallPermissionsPrompt(
     Extension* extension) {
   ExtensionInstallPrompt::Prompt prompt(
       ExtensionInstallPrompt::POST_INSTALL_PERMISSIONS_PROMPT);
   prompt.set_extension(extension);
   prompt.set_icon(LoadInstallPromptIcon());
   return prompt;
 }
 
 }  // namespace chrome