[gold] Search for closest diffs in parallel
[gold] Search for closest diffs in parallel

Bug: skia:10582
Change-Id: I2aacc7484b3a1588648c4c34fd31997d46366440
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/405636
Reviewed-by: Leandro Lovisolo <f558143c2568be8d55575d13f30a1fc5cb8009d5@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot