[IndexedDB] setVersion blocked on uncollected garbage IDBDatabases

We're currently implementing the onblocked/setVersion semantics and ran into
an interesting problem: if you don't call .close() on a database and simply
expect it to be collected, then you ever being able to run a setVersion
transaction is at the mercy of the garbage collecter doing a collection.
 Otherwise implementations will assume the database is still open...right?

If so, this seems bad.  But I can't think of any way to get around it.
 Thoughts?

J