Merge "Add shell background executor to bubbles and put unregister call on it"...

Merge "Add shell background executor to bubbles and put unregister call on it" into tm-dev am: 0fe75d50

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/18300851



Change-Id: I9118bd94acac735fd39397b3fe66dda5b13a3124
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>