adding the Chrome gardener

AFAICT neither the browser_bridge.js code for isSandboxedForTesting() nor the  security_SandboxStatus autotest have changed for long time.

the gpuInfo code whose data seems to be used by the javascript above has changed around the timeframe of the failure:
https://chromium-review.googlesource.com/#/c/chromium/src/+/887349/
Cannot spot anything bad though but that's Chrome code, not anything I know

zmo@, looks like your CL (https://chromium-review.googlesource.com/#/c/chromium/src/+/887349/) could be the cause of the failure.

Particularly, in GpuDataManagerImplPrivate::UpdateGpuInfo, the |sandboxed| flag was kept when gpu info is updated. Think this would propagate down and could cause chrome://gpu page to return false for browserBridge.isSandboxedForTesting().

Please check. Thanks.

Thanks zmo@ for the quick fix.

Fix in CQ now: https://chromium-review.googlesource.com/c/chromium/src/+/892088

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/48e31c1abc9d016c0d07ad32906094a31dc16733

commit 48e31c1abc9d016c0d07ad32906094a31dc16733
Author: Zhenyao Mo <zmo@chromium.org>
Date: Tue Jan 30 04:21:20 2018

Fix the GPUIno.sandboxed bit update.

BUG= 806669 
TEST=affected bots
R=piman@chromium.org,xiyuan@chromium.org
NOTRY=true

Change-Id: I954fc1f5cdcffe4d55ff41927b9b33075c9fd616
Reviewed-on: https://chromium-review.googlesource.com/892088
Commit-Queue: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532748}
[modify] https://crrev.com/48e31c1abc9d016c0d07ad32906094a31dc16733/content/browser/gpu/gpu_data_manager_impl_private.cc

Need the CL to be rolled into chromeos for these bots to turn green.

Assign to xiyuan@ to keep an eye on the bots. When they turn green, please close the bug.

Thanks.

PFQ passed for chrome 66.0.3336.3.

e.g. 
https://luci-milo.appspot.com/buildbot/chromeos/tricky-chrome-pfq/4669