Split SkTRacy into SkTRacy and SkTRacyReffable.

Split SkTRacy into SkTRacy and SkTRacyReffable.

Looks like TSAN can't always suppress our existing implementation of SkTRacy
(what is turning here into SkTRacyReffable).  To minimize flakiness, use
SkTRacy where possible and SkTRacyReffable where necessary.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/497cda3a6b72b9cb390334e8756d38b4ffac044f

NOTRY=true
R=robertphillips@google.com, mtklein@google.com, reed@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/388503002