#import // https://w3c.github.io/user-timing/#dom-performancemark [Exposed=(Window,Worker), UseNewAKString] interface PerformanceMark : PerformanceEntry { constructor(DOMString markName, optional PerformanceMarkOptions markOptions = {}); readonly attribute any detail; }; // https://w3c.github.io/user-timing/#ref-for-dom-performancemarkoptions-1 dictionary PerformanceMarkOptions { any detail; DOMHighResTimeStamp startTime; };