Stop passing --test-launcher-print-test-stdio=always to sandbox_linux_unittests on 4 bots.

If we always want the output, we should add the flag in testing/buildbot/gn_isolate_map.pyl
or waterfalls.pyl for all bots, and not set this for a small arbitrary subset.

Bug: 843511
Change-Id: I8a1e1f32ec22da2b02bc05ac56ecee659b4448ee
Reviewed-on: https://chromium-review.googlesource.com/1136517
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575012}
3 files changed