Use goog.async.nextTick instead of goog.async.Delay

[goog.async.nextTick](https://code.google.com/p/closure-library/source/browse/closure/goog/async/nexttick.js) provides a faster way of running code on the next tick. From `nexttick.js`:

```javascript
/**
 * Fires the provided callbacks as soon as possible after the current JS
 * execution context. setTimeout(…, 0) always takes at least 5ms for legacy
 * reasons.
 * ...
 */
```

This PR uses `goog.async.nextTick` instead of `goog.async.Delay` (`setTimeout`) for low-priority post-render functions.