克隆 IntervalHistogram

<IntervalHistogram> 实例可以通过 <MessagePort> 克隆。 在接收端，直方图被克隆为没有实现 enable() 和 disable() 方法的普通 <Histogram> 对象。

<IntervalHistogram> instances can be cloned via <MessagePort>. On the receiving end, the histogram is cloned as a plain <Histogram> object that does not implement the enable() and disable() methods.