code: function() {
          if(this.active) {
              return false;
          }
          // register for event handlers defined on this class.
          var events = OpenLayers.Events.prototype.BROWSER_EVENTS;
          for (var i=0, len=events.length; i<len; i++) {
              if (this[events[i]]) {
                  this.register(events[i], this[events[i]]); 
              }
          } 
          this.active = true;
          return true;
      }
docs: APIMethod: activate
  Turn on the handler.  Returns false if the handler was already active.
  
  Returns:
  {Boolean} The handler was activated.