Replace AutoClear with SK_AT_SCOPE_EXIT.

Change-Id: I218429246da2da3e80fb1823241fdbcf84f0dd30
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/372478
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
1 file changed