read network response within chrome extension
chrome.devtools.network.onRequestFinished.addListener(request => {
  request.getContent((body) => {
    if (request.request && request.request.url) {
      if (request.request.url.includes('facebook.com')) {
         //continue with custom code
         var bodyObj = JSON.parse(body);//etc.
      }
}
});
});
