code: function () {
              var me = this,
                  doc = me.document,
                  win = me.window;
              me._proxyDomEvent = utils.bind(me._proxyDomEvent, me);
              domUtils.on(doc, ['click', 'contextmenu', 'mousedown', 'keydown', 'keyup', 'keypress', 'mouseup', 'mouseover', 'mouseout', 'selectstart'], me._proxyDomEvent);
              domUtils.on(win, ['focus', 'blur'], me._proxyDomEvent);
              domUtils.on(me.body,'drop',function(e){
                  //阻止ff下默认的弹出新页面打开图片
                  if(browser.gecko && e.stopPropagation) { e.stopPropagation(); }
                  me.fireEvent('contentchange')
              });
              domUtils.on(doc, ['mouseup', 'keydown'], function (evt) {
                  //特殊键不触发selectionchange
                  if (evt.type == 'keydown' && (evt.ctrlKey || evt.metaKey || evt.shiftKey || evt.altKey)) {
                      return;
                  }
                  if (evt.button == 2)return;
                  me._selectionChange(250, evt);
              });
          }
docs: 初始化UE事件及部分事件代理
  @method _initEvents
  @private