code: function (callback, args) {
      microtickQueue.push([callback, args]);
      if (needsNewPhysicalTick) {
          schedulePhysicalTick();
          needsNewPhysicalTick = false;
      }
  }
docs: Configurable through Promise.scheduler. Don't export because it would be unsafe to let unknown code call it unless they do try..catch within their callback. This function can be retrieved through getter of Promise.scheduler though, but users must not do Promise.scheduler = myFuncThatThrowsException