Add FilePath to base namespace.

chromeos/chromeos_test_utils.h

 // 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.
 
 #ifndef CHROMEOS_CHROMEOS_TEST_UTILS_H_
 #define CHROMEOS_CHROMEOS_TEST_UTILS_H_
 
 #include <string>
 
+namespace base {
 class FilePath;
+}
 
 namespace chromeos {
 namespace test_utils {
 
 // Returns the path to the given test data file for this library.
 bool GetTestDataPath(const std::string& component,
                      const std::string& filename,
-                     FilePath* data_dir);
+                     base::FilePath* data_dir);
 
 }  // namespace test_utils
 }  // namespace chromeos
 
 #endif  // CHROMEOS_CHROMEOS_TEST_UTILS_H_