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This adds experimental test suites I can call from my new LUCI
bots.

Depends on a change which makes variable substitutions available
to gtests.

Bug: chromium:877018
Change-Id: Iadf529513e5a92a4e731d3adcaff874101356646
Reviewed-on: https://chromium-review.googlesource.com/1186412
Commit-Queue: Patrik Höglund <phoglund@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586243}