wtfStartTimeRangelink
Used to mark Async start. Async are similar to scope but they don't have to be strictly nested. The return value is used in the call to [endAsync]. Async ranges only work if WTF has been enabled.
说明
someMethod() { var s = wtfStartTimeRange('HTTP:GET', 'some.url'); var future = new Future.delay(5).then((_) { wtfEndTimeRange(s); }); }