docs: function injectLibraries(iframe, libs) {
          var headNode;
          var scriptNode;
          var libIdx, lib;
  
          headNode = W.getIFrameAnyChild(iframe);
  
          for (libIdx = 0; libIdx < libs.length; libIdx++) {
              lib = libs[libIdx];
              scriptNode = document.createElement('script');
              scriptNode.className = 'injectedlib';
              scriptNode.src = lib;
              headNode.appendChild(scriptNode);
          }
      }