Merge "Add background executor fow WmShell" into tm-dev am: a73a4428 am: 9a84714b am: f5ad7304

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/17693175



Change-Id: I6f534eec9bef1607fa957e43a6080c61fe44f0a8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>