code: function( className )
  		{
  			var c = this.$.className;
  			if ( c )
  			{
  				var regex = new RegExp( '(?:^|\\s)' + className + '(?:\\s|$)', '' );
  				if ( !regex.test( c ) )
  					c += ' ' + className;
  			}
  			this.$.className = c || className;
  		}
docs: Adds a CSS class to the element. It appends the class to the
  already existing names.
  @param {String} className The name of the class to be added.
  @example
  var element = new CKEDITOR.dom.element( 'div' );
  element.addClass( 'classA' );  // &lt;div class="classA"&gt;
  element.addClass( 'classB' );  // &lt;div class="classA classB"&gt;
  element.addClass( 'classA' );  // &lt;div class="classA classB"&gt;