Merge "Add OWNERS for back navigation files in WMShell." into tm-qpr-dev am: 5b1020a99d am: a1253ca231

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20425870

Change-Id: I9976e92ff40650ef9128a4c192c8aa2a1d2c7bd5
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>