message: Add addEventHandler
diff: var contentSideexTabId = -1;
  var frameLocation = "";
  +function Recorder(window) {
  + this.window = window;
  + this.attach();
  + this.dettach();
  +}
  +
  +Recorder.eventHandlers = {};
  +Recorder.addEventHandler = function(handlerName, eventName, handler, options) {
  + handler.handlerName = handlerName;
  + if (!options) options = false;
  + let key = options ? ('C_' + eventName) : eventName;
  + if (!this.eventHandlers[key]) {
  + this.eventHandlers[key] = [];
  + }
  + this.eventHandlers[key].push(handler);
  +}
  +
  +Recorder.prototype.attach = function() {
  +
  +}
  +
  // show element
  function startShowElement(message, sender, sendResponse){
  if (message.showElement) {
  