readable._destroy(err, callback)
err<Error> 可能的错误。callback<Function> 采用可选的错误参数的回调函数。
_destroy() 方法由 readable.destroy() 调用。
它可以被子类覆盖,但不能直接调用。
err<Error> A possible error.callback<Function> A callback function that takes an optional error argument.
The _destroy() method is called by readable.destroy().
It can be overridden by child classes but it must not be called directly.