public static <X> X waitFor(Callable<X> until) {
    return waitFor(until, DEFAULT_TIME_OUT, DEFAULT_UNIT);
  }
Wait for the callable to return either "not null" or "true". Exceptions are caught and only
rethrown if we time out.

@param until Condition that we're waiting for.
@return Whatever the condition returns.
selendroid-client/src/main/java/io/selendroid/client/waiter/TestWaiter.java