Add initial support for simple concave shadows.

Adds support for spot shadow outlines. Since filling the penumbra still
needs to be done, this code is disabled for now.

Bug: skia:
Change-Id: I3369eb13832b47ad16dd29ce7c7d6a1a10b39aeb
Reviewed-on: https://skia-review.googlesource.com/22363
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
5 files changed