Reset user data directory and disk cache directory after downgrade.

chrome/browser/policy/policy_path_parser_linux.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 <pwd.h>
 #include <stddef.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include "chrome/browser/policy/policy_path_parser.h"
@@ skipping 42 matching lines @@
   }
   return result;
 }
 
 void CheckUserDataDirPolicy(base::FilePath* user_data_dir) {
   // This function is not implemented in Linux because we don't support the
   // policy on this platform.
   NOTREACHED();
 }
 
+void CheckDiskCacheDirPolicy(base::FilePath* user_data_dir) {
+  // This function is not implemented in Linux because we don't support the
+  // policy on this platform.
+  NOTREACHED();
+}
+
 }  // namespace path_parser
 
 }  // namespace policy