Observed Chrome Bugs

Note: These are bugs with the Chrome browser itself, and not with our SDK.

1. PushManager.subscribe() will sometimes neither resolve nor reject its Promise. It will hang indefinitely.
2. A notification is said to be received (both by chrome://gcm-internals and our own service worker logging), but a notification is not visible. Somehow, showing a local notification (e.g. new Notification('hi')) suddenly makes both the local and push notification visible. Push notifications work after this hack just fine.
3. Notifications sometimes don't close on Chrome even when click X. They'll be stuck. You have to quit Chrome for the notifications to go away.
4. Notifications don't appear after opening the browser or waking from sleep, sometimes for many minutes, until a push notification is sent. Sounds like some optimization is going on there with regards to how Chrome is limiting polling.