Spot the mistake!

gistfile1.js

	(function (fn) {
		var callbacks = [];
		fn.draw = function (op) {
			var deferred = $.Deferred();

			op = op.bind(this);
			requestAnimationFrame(function () {
				op();
				callbacks.forEach(function (callback) { callback(); });
				deferred.resolve();
			});

			return deferred;
		}
		fn.onDraw = function (callback) {
			callback = callback.bind(this);
			callbacks.push(callback);
		};
	})(View.prototype);