Reset user data directory and disk cache directory after downgrade.

chrome/browser/policy/policy_path_parser.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 CHROME_BROWSER_POLICY_POLICY_PATH_PARSER_H_
 #define CHROME_BROWSER_POLICY_POLICY_PATH_PARSER_H_
 
 #include <string>
 
 #include "base/files/file_path.h"
@@ skipping 46 matching lines @@
 // any policy infrastructure. This is required because this policy is needed
 // much earlier before the PrefService is initialized.
 // The function will fill |user_data_dir| if the policy "UserDataDir" is set and
 // leave it intact if the policy is missing. If the policy is set it should
 // override any manual changes to the profile path the user might have made so
 // this function should be used to verify no policy is specified whenever the
 // profile path is not read from the PathService which already takes this into
 // account.
 void CheckUserDataDirPolicy(base::FilePath* user_data_dir);
 
+#if defined(OS_WIN)

[grt (UTC plus 2), 2016/05/19 23:39:27]

although it's only used on Win, it's cleaner to declare/define it on all
platforms

[zmin, 2016/05/20 00:52:25]

Done. But I'll leave Linux/Mac version as unimplemented because no one will use
this function on those platform.

[grt (UTC plus 2), 2016/05/20 15:25:04]

Acknowledged.

+// A helper function used to read the DiskCacheDir path policy without relying
+// on any policy infrastructure. This is required because this policy may be
+// needed much earlier before the PrefService is initialized on Windows.
+// The function will fill |disk_cache_dir| if the policy "DiskCacheDir" is set
+// and leave it intact if the policy is missing.
+void CheckDiskCacheDirPolicy(base::FilePath* disk_cache_dir);
+#endif
+
 }  // namespace path_parser
 
 }  // namespace policy
 
 #endif  // CHROME_BROWSER_POLICY_POLICY_PATH_PARSER_H_