Cache issue with crossorigin, 'vary: *' Responses

• Component: Service Workers
• Status: NEW ---

[Lion Ralfs]

When attempting to add requests to the cache via the CacheStorage API (https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage), 
any request that results in a response with the response header 'vary: *' causes the operation to fail with an error:

"TypeError: Response has a '*' Vary header value"

I'm assuming that this is the expected behavior.

However, when adding a _crossorigin_ request with a 'vary: *' header, no error is thrown.

Instead, Safari adds the cache entry without replacing previous entries with the same URL. This becomes evident by repeatedly reloading a page that attempts to add a crossorigin, 'vary: *' request to the cache.
If one reads the cache after a few page-reloads (via `cache.matchAll` for example), the same response is returned multiple times.

I've isolated a test case in this repository: https://github.com/lionralfs/caches-vary-crossorigin-behavior

1. Run `npm install`
2. Run `npm start`
3. Visit localhost:8000 in Safari
4. Reload the page a few times
5. Click the button to read the cache which displays the cache entries
6. Take a look at the index.html for details

To be honest, I'm not entirely sure what the expected behavior is for crossorigin + 'vary: *' responses and I've file a Chrome bug as well (since they have a similar issue): https://bugs.chromium.org/p/chromium/issues/detail?id=1274098

[Radar WebKit Bug Importer]

<rdar://problem/86103155>