[ServiceWorker] Timing of events relative to initial script load (#605)

Let's say I have the following worker:

```javascript
var myCache;
caches.open('my-cache').then(function (cache) {
  myCache = cache;
});

self.oninstall = function(event) {
  myCache.add('index.html');
};
```

Are there any guarantees about the order of operations? Specifically, will the promise created during script load, that sets the `myCache` variable, be resolved before the `install` event is triggered?

I'm guessing that, no, this is a race condition, and you can't rely on it. But it limits the useful setup work that can be done when a script is restarted. You can't defer boilerplate stuff to `install` or `activate` for scripts that are just being restarted.

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Reply to this email directly or view it on GitHub:
https://github.com/slightlyoff/ServiceWorker/issues/605