Retrieving lots of rows from IndexedDB. Warning - this will load ~180mb of JSON from ~100k rows files.

1. Fetch + write to IndexedDB - download 190mb of JSON and store it across ~100k rows in IndexedDB
2. Load IDBObjectStore.openCursor - load all ~100k rows using store.openCursor
3. Load IDBIndex.openCursor - load all ~100k rows using index.openCursor

Check the JS console for errors - this is just a simple repro :)