Few improvements on Augmented Autofill.

- Send the initial value of the focused field, so the service can decide whether
  or not to display the autofill UI if it's not empty.
- Log how long it took for the service to handle the request and to hte system
  to render the UI.
- Use CloseGuard to make sure the UI is properly destroyed.

Bug: 120303290
Bug: 119638877

Test: manual verification

Change-Id: I7abed10c0915ff9a2deddb488c70e1491cdbd480