Move ReadFileToString to the base namespace.

chrome/browser/chromeos/extensions/file_manager/file_manager_browsertest.cc

 // Copyright (c) 2013 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.
 
 // Browser test for basic Chrome OS file manager functionality:
 //  - The file list is updated when a file is added externally to the Downloads
 //    folder.
 //  - Selecting a file and copy-pasting it with the keyboard copies the file.
 //  - Selecting a file and pressing delete deletes it.
 
@@ skipping 232 matching lines @@
                   const std::string& mime_type,
                   bool shared_with_me,
                   const base::Time& modification_time) {
     google_apis::GDataErrorCode error = google_apis::GDATA_OTHER_ERROR;
 
     std::string content_data;
     if (!source_file_name.empty()) {
       base::FilePath source_file_path =
           google_apis::test_util::GetTestFilePath("chromeos/file_manager").
               AppendASCII(source_file_name);
-      ASSERT_TRUE(file_util::ReadFileToString(source_file_path, &content_data));
+      ASSERT_TRUE(base::ReadFileToString(source_file_path, &content_data));
     }
 
     scoped_ptr<google_apis::ResourceEntry> resource_entry;
     fake_drive_service_->AddNewFile(
         mime_type,
         content_data,
         fake_drive_service_->GetRootResourceId(),
         target_file_name,
         shared_with_me,
         google_apis::test_util::CreateCopyResultCallback(&error,
@@ skipping 311 matching lines @@
                       TestParameter(NOT_IN_GUEST_MODE, "shareDirectory")));
 
 INSTANTIATE_TEST_CASE_P(
     restoreGeometry,
     FileManagerBrowserTest,
     ::testing::Values(TestParameter(NOT_IN_GUEST_MODE, "restoreGeometry"),
                       TestParameter(IN_GUEST_MODE, "restoreGeometry")));
 
 }  // namespace
 }  // namespace file_manager