Several clients have asked for support of send-to-sync notifications, where a notification is received and the device is expected to sync down the new data in the background in response to the notification (instead of the notification itself carrying the payload).

My understanding from @collinjackson is that this is not currently possible to wire up due to lack of headless-Dart support in our APIs exposed to Flutter plugins.

This issue tracks work in the engine. Providing APIs to access the engine support is tracked in #3671