IndexedDB does not persist in WKWebView after closing app

I realize y'all are actively developing WKWebView support. This may be a bug in WKWebView itself, or maybe in Cordova; I'm not sure. Hence this bug report.

Video demonstration

Steps to repro:

1. Install my database filler app
2. Follow the instructions to run the WKWebView branch
3. Open up the XCode project in platforms/ios
4. Run on a real device
5. Open up the app, add some data, count it to make sure items were added.
6. Double-press the home button to dismiss the app
7. Reopen it, count items

*Expected*: items that were saved in IndexedDB before are still there.

*Actual*: 0 items are found.