ShadowUtils: Fix umbra inset calculation when determining if umbra is fully occluded.

Change-Id: Id0db49ad45b341d39abf7ee532ecc0799a832192
Reviewed-on: https://skia-review.googlesource.com/8079
Commit-Queue: Stan Iliev <stani@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
1 file changed