IndexedDB should be closed before delete

[puzrin]

Type of bug

• Differences between Can I use & Modernizr
• False positive
• Modernizr error

Describe the bug

Modernizr/feature-detects/storage/indexeddb.js

Line 52 in 28d969e

detectDeleteDatabase(indexeddb, testDBName);

IndexedDB should be closed before delete. In other case delete request is postponed until page close.

req.result.close should help. I'm not sure about previous place (how to get opened connection there)

How to Reproduce

Difficult to show with existing code, because Modernized does not wait for result of delete. But in other, implementation, if you wait for result, code will hand on opened database https://github.com/nodeca/bkv/blob/master/src/idb_storage.mjs#L56. Need comment from someone experienced with IndexedDB, why that branch exists at all.

Expected behavior

Testing DB should be deleted immediately.

Additional context

Also, not sure why Modernizr creates random db on every use. If db already exists, that's probably "success".