Fix b/5392171 and b/5389281.

1. Fix b/5392171 by moving effect context creation into Filter to make
sure it'd be created when needed.
2. Revise the fix for b/5389281 by clearing surface background even
there's no photo.

Change-Id: I212a552291c7df28b75a909bf6560634ba061e9f
4 files changed