code: function (msg) {
              var i,
                  sheet,
                  text = "";
              for (i = 0; i < window.document.styleSheets.length; i++) {
                  sheet = window.document.styleSheets[i];
                  // if it was already 'reloaded'
                  if (sheet.ownerNode.id ===  msg.params.url) {
                      text = sheet.ownerNode.textContent;
                  } else if (sheet.href === msg.params.url && !sheet.disabled) {
                      var j,
                          rules;
  
                      // Deal with Firefox's SecurityError when accessing sheets
                      // from other domains, and Chrome returning `undefined`.
                      try {
                          rules = window.document.styleSheets[i].cssRules;
                      } catch (e) {
                          if (e.name !== "SecurityError") {
                              throw e;
                          }
                      }
                      if (!rules) {
                          return;
                      }
  
                      for (j = 0; j < rules.length; j++) {
                          text += rules[j].cssText + '\n';
                      }
                  }
              }
  
              MessageBroker.respond(msg, {
                  text: text
              });
          }
docs: retrieves the content of the stylesheet
  TODO: it now depends on reloadCSS implementation