virtgpu_crosdomain: add metadata_cache_lock

crosdomain specific metadata_cache should be protected by a backend
specific lock to reduce lock contention.

BUG=b:201110412
TEST=CQ

Change-Id: Ic3cedd7ad7903e669f7fba2b5f45d88739fbdc97
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/minigbm/+/3188471
Commit-Queue: Yiwei Zhang <zzyiwei@chromium.org>
Tested-by: Yiwei Zhang <zzyiwei@chromium.org>
Reviewed-by: Chia-I Wu <olv@google.com>
2 files changed