In G1ParTask::work() there is a comment:

      // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
      // treating the nmethods visited to act as roots for concurrent marking.
      // We only want to make sure that the oops in the nmethods are adjusted with regard to the
      // objects copied by the current evacuation.

That one has been in the wrong place for some time. Move it to correct place.