youTubeIFrameInject.js

//  Append a script to the page which will intercept YouTube's server requests and post messages out of the iframe with details about those requests.
//  Needs to be an injected script because content scripts are sandboxed in such a way that they do not share variables with appended scripts.
this.injectInterceptorScript = function() {
  var interceptorScript = document.createElement('script');
  interceptorScript.src = chrome.runtime.getURL('js/inject/interceptor.js');
  document.head.appendChild(interceptorScript);
}.bind(this);