Move ReadFileToString to the base namespace.

chrome/browser/chromeos/drive/file_system_unittest.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 "chrome/browser/chromeos/drive/file_system.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 731 matching lines @@
   // The opened file is downloaded, which means the file is available
   // offline. The directory change should be notified so Files.app can change
   // the offline availability status of the file.
   ASSERT_EQ(1u, mock_directory_observer_->changed_directories().size());
   EXPECT_EQ(base::FilePath(FILE_PATH_LITERAL("drive/root")),
             mock_directory_observer_->changed_directories()[0]);
 
   // Verify that the file contents match the expected contents.
   const std::string kExpectedContent = "This is some test content.";
   std::string cache_file_data;
-  EXPECT_TRUE(file_util::ReadFileToString(opened_file_path, &cache_file_data));
+  EXPECT_TRUE(base::ReadFileToString(opened_file_path, &cache_file_data));
   EXPECT_EQ(kExpectedContent, cache_file_data);
 
   FileCacheEntry cache_entry;
   EXPECT_TRUE(cache_->GetCacheEntry(file_resource_id, &cache_entry));
   EXPECT_TRUE(cache_entry.is_present());
   EXPECT_TRUE(cache_entry.is_dirty());
 
   base::FilePath cache_file_path;
   EXPECT_EQ(FILE_ERROR_OK, cache_->GetFile(file_resource_id, &cache_file_path));
   EXPECT_EQ(cache_file_path, opened_file_path);
@@ skipping 104 matching lines @@
       kEmbedOrigin,
       google_apis::test_util::CreateCopyResultCallback(&error, &share_url));
   test_util::RunBlockingPoolTask();
 
   // Verify the error and the share url, which should be empty.
   EXPECT_EQ(FILE_ERROR_FAILED, error);
   EXPECT_TRUE(share_url.is_empty());
 }
 
 }   // namespace drive