clean up caches at thread exit

Change-Id: I9012a2769eb92d0d393e0eeb684a8bee8519323d
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/266522
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed