code: function (aButtons, iIndex) {
  			for (var i0 = iIndex - 1; i0 >= 0; i0--) {
  				if (this._setFocusOnButton(aButtons[i0])) {
  					return;
  				}
  			}
  
  			for (var i1 = aButtons.length - 1; i1 >= iIndex; i1--) {
  				if (this._setFocusOnButton(aButtons[i1])) {
  					return;
  				}
  			}
  		}
docs: Sets focus on previous button
  @param {Array} aButtons the array of Buttons
  @param {int} iIndex the index of the currently focused buttons