function startListening() {
  const caller =
      new goog.messaging.PortCaller(new goog.messaging.PortChannel(self));

  caller.dial('frame').registerService('sendToMain', function(msg) {
    'use strict';
    msg.push('worker1');
    caller.dial('main').send('result', msg);
  }, true);
}
@fileoverview A web worker for integration testing the PortPool class.

@nocompile