SF: Set dirty region bit if transparent region hint changes

We need to recompute visible regions if the transparent hint changes.
Previously we were relying incorrectly on metadata change to
recompute visible region. Since we set metadata every frame, we were
always forcing visible regions to be recomputed.

Test: check steps in bug does not repro
Fixes: 191954056
Change-Id: Idd3adf7cf950a3655a5d8593da2f5aa0adcbbca1