code: public void removeCallbacks(Runnable r) {
          assert handler != null;
          if (!sanityCheck("removeCallbacks " + r)) {
              return;
          }
          handler.removeCallbacks(r);
      }
docs: Remove any pending posts of {@link Runnable} {@code r} that are in the
  message queue.
  
  @param r
  {@code Runnable} to remove from queue.