src/js/controls/Header.js
function( isClosable ) {
		this._canDestroy = isClosable || this.tabs.length > 1;
		if( this.closeButton && this._isClosable() ) {
			this.closeButton.element[ isClosable ? "show" : "hide" ]();
			return true;
		}

		return false;
	}
function( isClosable ) {
		this._canDestroy = isClosable || this.tabs.length > 1;
		if( this.closeButton && this._isClosable() ) {
			this.closeButton.element[ isClosable ? "show" : "hide" ]();
			return true;
		}

		return false;
	}
function ( isClosable ) { this . _canDestroy = isClosable || this . tabs . length > 1 ; if ( this . closeButton && this . _isClosable ( ) ) { this . closeButton . element [ isClosable ? "show" : "hide" ] ( ) ; return true ; } return false ; }
Programmatically set closability.

@package private
@param {Boolean} isClosable Whether to enable/disable closability.

@returns {Boolean} Whether the action was successful
Programmatically set closability .