[autoroll] Add libcxxabi => Chromium roller
[autoroll] Add libcxxabi => Chromium roller

Possible after https://chromium-review.googlesource.com/c/chromium/src/+/2729355

Bug: chromium:1177288
Change-Id: I875875c76fa8ad80ab6cc4ce2f215145822ab0dc
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/378516
Auto-Submit: Nico Weber <c0f02d98506190746d1cdcb01be0f37b51e27077@chromium.org>
Commit-Queue: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@google.com>
Reviewed-by: Eric Boren <0e499112533c8544f0505ea0d08394fb5ad7d8fa@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