Fix skia_use_ffmpeg builds

... post https://skia-review.googlesource.com/c/skia/+/317109

Change-Id: I7286fd6d7598a50a1db452f04a28317c600f4984
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/318477
Commit-Queue: Adlai Holler <adlai@google.com>
Auto-Submit: Florin Malita <fmalita@chromium.org>
Reviewed-by: Adlai Holler <adlai@google.com>
2 files changed