function Loop(func) {
	    var useClock = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : true;

	    classCallCheck(this, Loop);

	    this.func = func;
	    this.clock = useClock ? new Clock() : null;
	    this.enabled = false;
	  }
@class Loop
@category core
@param {Function} func function to execute on each animation frame
@param {Boolean} [useClock=true] passes a Clock to the function when called, if true
@memberof module:core