virtio: video: fix broken test
virtio: video: fix broken test

http://crrev.com/c/3676695 removed the `anon` constructor from
SharedMemory. Update the test that uses it.

BUG=None
TEST=cargo test --features "video-decoder,ffmpeg" -p devices virtio::video

Change-Id: Ic4d8a48d2466dc35c47422cd89f9d99d031e2d1a
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3685673
Commit-Queue: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>
Reviewed-by: Junichi Uekawa <6bd240a6ce32463e272bb69c685a8e946b33ac05@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

google/crosvm,google/crosvm,google/crosvm,google/crosvm