Add desktopui_CrashyReboot{Server} autotest

To address some GPU hanging problems, we added logic to reboot the
device if the UI seemed to crash too much, too often.
This server-side test validates this logic by deploying an
associated client-side test to the DUT that drives it into
the failure state.

CQ-DEPEND=CL:65243
BUG=chromium:261784
TEST=run this autotest, and it should succeed.
TEST=run this autotest and while it's running, echo $(date +%s) > /var/lib/ui/reboot-timestamps. The test should fail.

Change-Id: I68af57e0266e85434ad63e1f646e90a41a6d393d
Reviewed-on: https://gerrit.chromium.org/gerrit/65218
Tested-by: Chris Masone <cmasone@chromium.org>
Reviewed-by: Richard Barnette <jrbarnette@chromium.org>
Commit-Queue: Chris Masone <cmasone@chromium.org>
9 files changed