Plumb layer style parsing, and extend existing DropShadowAdapter to
support both drop shadow style and drop shadow effect.
Change-Id: Id99a419dacd06dc38dc4cf84ff4ecb92218c45f7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/279020
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>