[tricium] Set -tricium git attributes for chromium

This would disable Tricium* running jobs on files in third_party/,
with the exception of third_party/blink/, which should be analyzed
except for web test expectation files.

* https://chromium.googlesource.com/infra/infra/+/master/go/src/infra/tricium

Bug: 904007
Change-Id: I5369a20cc42417756430adc46f9efe0114b7f385
Reviewed-on: https://chromium-review.googlesource.com/c/1394935
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Marc-Antoine Ruel <maruel@chromium.org>
Commit-Queue: Marc-Antoine Ruel <maruel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623674}
2 files changed