code: function styleForURL(url) {
          var styleSheetId, styles = {};
          url = _canonicalize(url);
          for (styleSheetId in _styleSheetDetails) {
              if (_styleSheetDetails[styleSheetId].canonicalizedURL === url) {
                  styles[styleSheetId] = _styleSheetDetails[styleSheetId];
              }
          }
          return styles;
      }
docs: Get the style sheets for a url
  @param {string} url
  @return {Object.<string, CSSStyleSheetHeader>}