code: function(size, units) {
              // Most common case first: Size is set to a number
              if (typeof size == 'number') {
                  return size + (units || this.defaultUnit || 'px');
              }
  
              // Size set to a value which means "auto"
              if (size === "" || size == "auto" || size === undefined || size === null) {
                  return size || '';
              }
  
              // Otherwise, warn if it's not a valid CSS measurement
              if (!this.unitRe.test(size)) {
                  //<debug>
                  if (Ext.isDefined(Ext.global.console)) {
                      Ext.global.console.warn("Warning, size detected as NaN on Element.addUnits.");
                  }
                  //</debug>
                  return size || '';
              }
  
              return size;
          }
docs: Test if size has a unit, otherwise appends the passed unit string, or the default for this Element.
  @param size {Object} The size to set
  @param units {String} The units to append to a numeric size value
  @private
  @static