Add logging reasons to WmLsVis.

Logging reasons for scene changes is something flexi does really well, and this particular boolean is important enough that I think it's worth a bit of extra log overhead to know why it's being set. I've manually added a subset of these many times to figure out bugs, and bug reports will be far more actionable with this information.

Bug: 439671061
Test: logging change (but tests do pass)
Flag: EXEMPT logging change
Change-Id: I3ec0bf947f429a231858738f8d1b6942e39bfcc3