code: function (button, cb) {
              var lastPosition = this._lastMousePosition;
              this._sendEvent('mousedown', lastPosition.x, lastPosition.y, this.BUTTONS[button]);
              this._callCallback(cb);
          }
docs: Simulates a mouse button press.
  @param {Number} button Button to be pressed (should be the value of aria.jsunit.Robot.BUTTONx_MASK, with x
  replaced by 1, 2 or 3).
  @param {aria.core.CfgBeans:Callback} callback