Revert^2 "Make isBackDisabled() not SystemAPI"

This reverts commit 5c099e29c6d06bd3b5f1c5665cf5c670c5fdbb46.

Reason for revert: This revert was accidentally submitted and is needed.

Change-Id: I07be2f5a27a8eedc88d93b5d3678a96e5efa2a24
2 files changed