Buggy looking null check in ServiceThread::oops_do()

void ServiceThread::oops_do(OopClosure* f, CodeBlobClosure* cf)

Passes both OopClosure and CodeBlobClosure but doesn't call JvmtiDeferredMethodQueue::oops_do() if cf is NULL, ignoring the OopClosure passed in. The latter doesn't use 'f' but ServiceThread shouldn't know that.