This property getter must be called with the PerformanceResourceTiming object as the receiver.
PerformanceResourceTiming
新增于: v18.2.0, v16.17.0
表示启动重定向的抓取开始时间的高分辨率毫秒时间戳。
【The high resolution millisecond timestamp that represents the start time of the fetch which initiates the redirect.】