fix clang-tidy make_unique warning

No-Try: true
TBR=johnstiles@google.com
Change-Id: Ie545a6b9b713d0caba5bdf2fcb118b71b8e5c369
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/307716
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
1 file changed