code: function() {
          this.logger.log("focus");
          this.valueChangeSource = Slider.SOURCE_UI_EVENT;
  
          // Focus the background element if possible
          var el = this.getEl();
  
          if (el.focus) {
              try {
                  el.focus();
              } catch(e) {
                  // Prevent permission denied unhandled exception in FF that can
                  // happen when setting focus while another element is handling
                  // the blur.  @TODO this is still writing to the error log 
                  // (unhandled error) in FF1.5 with strict error checking on.
              }
          }
  
          this.verifyOffset();
  
          return !this.isLocked();
      }
docs: Try to focus the element when clicked so we can add
  accessibility features
  @method focus
  @private