Merge "Update deprecation documentation for onBackPressed" into tm-dev am: 4f774309 am: adb7c463 am: 25f03fe9

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/18090442



Change-Id: Iabdd5f150c2e59e5dd2078db76676f79e409cbb2
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>