title: Monitor network with headless chrome
body: <p>I'm exciting to use headless chrome, I want some function like <code>onResourceRequested</code> in <a href="http://phantomjs.org/network-monitoring.html" rel="nofollow noreferrer">Phatom.js</a>.</p>
  
  <p>But I did not find the corresponding function for monitoring the HttpRequest. after check the <a href="https://chromedevtools.github.io/devtools-protocol/tot/Network/" rel="nofollow noreferrer">dev tools documentation</a>, I find many function use <code>requestId</code>, but there is not even a function for getting such an Id, how do you do the network monitoring?</p>