Function postMessage

packages/scheduler/src/__tests__/Scheduler-test.js:91–97

()

    const port1 = {};
    const port2 = {
      postMessage() {
        if (hasPendingMessageEvent) {
          throw Error('Message event already scheduled');
        }
        log('Post Message');
        hasPendingMessageEvent = true;
      },
    };
    global.MessageChannel = function MessageChannel() {
      this.port1 = port1;