Move ReadFileToString to the base namespace.

chrome/test/perf/tab_switching_test.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 "base/command_line.h"
 #include "base/environment.h"
 #include "base/file_util.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/path_service.h"
@@ skipping 95 matching lines @@
       // Close the browser to force a dump of log.
       bool application_closed = false;
       EXPECT_TRUE(CloseBrowser(browser_proxy_.get(), &application_closed));
 
       // Open the corresponding log file and collect average from the
       // histogram stats generated for RenderWidgetHost_TabSwitchPaintDuration.
       bool log_has_been_dumped = false;
       std::string contents;
       int max_tries = 20;
       do {
-        log_has_been_dumped = file_util::ReadFileToString(log_file_name_,
-                                                          &contents);
+        log_has_been_dumped = base::ReadFileToString(log_file_name_, &contents);
         if (!log_has_been_dumped)
           base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(100));
       } while (!log_has_been_dumped && max_tries--);
       ASSERT_TRUE(log_has_been_dumped) << "Failed to read the log file";
 
       // Parse the contents to get average.
       int64 average = 0;
       const std::string average_str("average = ");
       std::string::size_type pos = contents.find(
           "Histogram: MPArch.RWH_TabSwitchPaintDuration", 0);
@@ skipping 65 matching lines @@
   RunTabSwitchingUITest("t", true);
 }
 
 // Started failing with a webkit roll in r49936. See http://crbug.com/46751
 TEST_F(TabSwitchingUITest, DISABLED_TabSwitchRef) {
   UseReferenceBuild();
   RunTabSwitchingUITest("t_ref", true);
 }
 
 }  // namespace