As a user, I'd like browser to automatically sync as I browse, so that my activity is available on my other devices

[grigoryk]

Now that we have SyncManager, let's start doing heuristic-based syncing. E.g. Fennec synced in response to ContentProvider changes (new bookmarks, browsing history, etc), except that the decision to auto-sync wasn't fully controlled by Fennec (Android's AccountManager handled scheduling synchronization in response to "we should sync soon" requests).