Method delay

src/service/timer-impl.js:53–85

* Runs the provided callback after the specified delay. This uses a micro * task for 0 or no specified time. This means that the delay will actually * be close to 0 and this will NOT yield to the event queue. * * Returns the timer ID that can be used to cancel the timer (cancel method).

(callback, opt_delay)

   * @return {number|string}
   */
  delay(callback, opt_delay) {
    if (!opt_delay) {
      // For a delay of zero,  schedule a promise based micro task since
      // they are predictably fast.
      const id = 'p' + this.taskCount_++;
      this.resolved_
        .then(() => {
          if (this.canceled_[id]) {
            delete this.canceled_[id];
            return;
          }
          callback();
        })
        .catch(reportError);
      return id;
    }
    const wrapped = () => {
      try {
        callback();
      } catch (e) {
        reportError(e);
        throw e;
      }
    };
    const index = this.win.setTimeout(wrapped, opt_delay);
    if (getMode().test) {
      if (!timersForTesting) {
        timersForTesting = [];
      }
      timersForTesting.push(index);
    }
    return index;
  }

  /**
   * Cancels the previously scheduled callback.