code: function (href) {
                  var self = this;
  
  
                  // Inspect CSSRules for @imports:
                  // styleSheet obejct is required to scan CSSImportRules but
                  // browsers differ on the implementation of MutationObserver interface.
                  // Webkit triggers notifications before stylesheets are loaded,
                  // Firefox does it after loading.
                  // There are also differences on when 'load' event is triggered for
                  // the 'link' nodes. Webkit triggers it before stylesheet is loaded.
                  // Some references to check:
                  //      http://www.phpied.com/when-is-a-stylesheet-really-loaded/
                  //      http://stackoverflow.com/questions/17747616/webkit-dynamically-created-stylesheet-when-does-it-really-load
                  //        http://stackoverflow.com/questions/11425209/are-dom-mutation-observers-slower-than-dom-mutation-events
                  //
                  // TODO: This is just a temporary 'cross-browser' solution, it needs optimization.
                  var loadInterval = setInterval(function () {
                      var i;
                      for (i = 0; i < window.document.styleSheets.length; i++) {
                          if (window.document.styleSheets[i].href === href) {
                              //clear interval
                              clearInterval(loadInterval);
                              // notify stylesheets added
                              self.notifyStylesheetAdded(href);
                              break;
                          }
                      }
                  }, 50);
              }
docs: Check the stylesheet that was just added be really loaded
  to be able to extract potential import-ed stylesheets.
  It invokes notifyStylesheetAdded once the sheet is loaded.
  @param  {string} href Absolute URL of the stylesheet.