[skottie] Annotation support for 'add' blending mode
[skottie] Annotation support for 'add' blending mode

(https://github.com/bodymovin/bodymovin-extension/commit/c78486873b7422ec374980b36f6403d33fb8978a)

Change-Id: I4f3724a57ee384c13b68db5960f89d387431f11c
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/208240
Commit-Queue: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Auto-Submit: Florin Malita <a8262bf13ea8c26821e91ea9bca6740a77c96dcd@chromium.org>
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot