[AndroidSms] Fix issue with background notifications after migration.

This CL fixes issue with background notifications not working after
PWA migration. This was caused due to StreamingConnectionEstablisher
not clearing state in TearDown. Also fixed related issue with stopping
service worker in TearDown.

Bug: 939581
Change-Id: Icfda555117fac726b39f34b8a601dc447c9d6ef5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1510655
Reviewed-by: Jeremy Klein <jlklein@chromium.org>
Commit-Queue: Azeem Arshad <azeemarshad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639129}
4 files changed