Reset user data directory and disk cache directory after downgrade.

chrome/browser/policy/policy_path_parser_linux.cc

Index: chrome/browser/policy/policy_path_parser_linux.cc
diff --git a/chrome/browser/policy/policy_path_parser_linux.cc b/chrome/browser/policy/policy_path_parser_linux.cc
index 9b0e6fd4d9d4e73fa7a85be3d2290bd1fe8aa0e1..a36417decbe8cec03882b76a36480b21421bd387 100644
--- a/chrome/browser/policy/policy_path_parser_linux.cc
+++ b/chrome/browser/policy/policy_path_parser_linux.cc
@@ -60,6 +60,12 @@ void CheckUserDataDirPolicy(base::FilePath* user_data_dir) {
   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