Reset user data directory and disk cache directory after downgrade.

chrome/browser/policy/policy_path_parser.h

Index: chrome/browser/policy/policy_path_parser.h
diff --git a/chrome/browser/policy/policy_path_parser.h b/chrome/browser/policy/policy_path_parser.h
index 7f4bab1235c8e7870d0dc6c9be11f34dabc61587..f1d30b38cf6197c2c9a9544c1fcca03ca27fcc16 100644
--- a/chrome/browser/policy/policy_path_parser.h
+++ b/chrome/browser/policy/policy_path_parser.h
@@ -64,6 +64,13 @@ base::FilePath::StringType ExpandPathVariables(
 // account.
 void CheckUserDataDirPolicy(base::FilePath* user_data_dir);
 
+// 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);
+
 }  // namespace path_parser
 
 }  // namespace policy