ThreeLeggedFlow oauthFlow = newFlow(userId);
oauthFlow.setJsonFactory(getJsonFactory());
oauthFlow.setHttpTransport(getHttpTransport());
try {
Credential cred = oauthFlow.loadCredential(pm);
if (cred != null && cred.isInvalid()) {
pm.deletePersistent(cred);
cred = null;
}