Add log when UMO is marked visible to user

We need to know if UMO is visible to user because seekbar should only
animate when it is visible to user. Currently on some devices, when AOD
screen shows up, seekbar animation does not stop. This should only
happen when UMO is visible to user.

Flag: NONE
Bug: 321570646
Test: Build
Change-Id: If905dabf8a2a4e83708a025c5986a02dc0b322ad