Add SYSTEM_FLAG_HIDE_NON_SYSTEM_OVERLAY_WINDOWS to CalendarDebugActivity am: 11fe2048a5 am: 26705a8da6

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/providers/CalendarProvider/+/13545483

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I110954378a9e1b7313e5a6c4ee8f6bc8d57b30c9