[skottie] Default camera for 3D layers

When 3D layers are present, we need a camera view even when no explicit
camera is present.

TBR=
Bug: skia:8914
Change-Id: I408986d516e03bc4f80c7c09103e09821704ff2f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/249420
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Florin Malita <fmalita@chromium.org>
3 files changed