Merge "Add background executor fow WmShell" into tm-dev am: a73a4428 am: cad0761e

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



Change-Id: I033b0b1d63d9b514a00b7e7c6062e6501c279599
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>