Due to a bug in the native `requestAnimationFrame` function running inside `<iframe>` elements on iOS 6, I've decided to write up a custom function that implements a blacklist. Use this snippet and use `nextFrame` and `cancelFrame` on the `window` object to use this workaround with the same method signature as the spec. I've avoided overriding the native functions in case you have other code that detects them. Adapted from http://paulirish.com/2011/requestanimationframe-for-smart-animating/

## raf.js
// requestAnimationFrame implementation as a custom function to allow blacklisting
// devices with broken implementation. Currently needs timer-based fallbacks for iOS 6.x for
// code running inside <iframe> elements.
// Uses polyfills based on http://paulirish.com/2011/requestanimationframe-for-smart-animating/
(function() {

    var blacklisted   = /iP(ad|hone|od).*OS 6/.test(window.navigator.userAgent),
        lastTime      = 0,
        nativeRequest = window.requestAnimationFrame || null,
        nativeCancel  = window.cancelAnimationFrame  || null;

    ['webkit', 'moz'].forEach(function(prefix) {
        nativeRequest = nativeRequest || window[prefix+'RequestAnimationFrame'] || null;
        nativeCancel  = nativeCancel  || window[prefix+'CancelAnimationFrame']  || window[prefix+'CancelRequestAnimationFrame'] || null;
    });

    function polyfillRequest(callback, element) {
        var currTime = new Date().getTime();
        var timeToCall = Math.max(0, 16 - (currTime - lastTime));
        var id = window.setTimeout(function() { callback(currTime + timeToCall); }, timeToCall);
        lastTime = currTime + timeToCall;
        return id;
    }

    function polyfillCancel(id) {
        clearTimeout(id);
    }

    this.nextFrame   = (!blacklisted && nativeRequest != null) ? nativeRequest : polyfillRequest;
    this.cancelFrame = (!blacklisted && nativeCancel  != null) ? nativeCancel  : polyfillCancel;

})();