I created crrev.com/c/1333102 and crrev.com/c/1333099 to add /etc/init/vivid.conf, which is an upstart script to load vivid.

Though Dan suggested to make vivid a built-in module in  crbug.com/899595#c18 , I chose a way of using upstart script because it won't break existing tests that unload vivid.
In addion, we might want to unload vivid manually for testing purpose.
e.g. we can test features detecting newly connected camera devices.

I also created crrev.com/c/1335058 to stop loading/unloading vivid in WebRTC tests.
This CL would not be necessary to make video.Capability pass on betty, because video.Capablity is executed before WebRTC tests (thanks to alphabetical order).
But, we should remove unnecessary code.


After these CLs, the followings can be TODOs:
(1) After Chrome's CHROMEOS_LKGM contains above changes, stop loading vivid for capture_unittests.
(2) Stop loading vivid in autotests' video_WebRtc* tests.

But, we won't need (1) if we create a Tast tests for capture_unittests in  Issue 900849 .
Also, I don't think (2) is needed because we can hopefully remove these tests in near future. 

> Though Dan suggested to make vivid a built-in module in  crbug.com/899595#c18 

s/Dan/Doug/ :-)

This sounds good to me. Thanks!

#2: Oops. Sorry, Dan and Doug!

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a81bdb917ecd5c3bd158865d35338a37ca300995

commit a81bdb917ecd5c3bd158865d35338a37ca300995
Author: Keiichi Watanabe <keiichiw@chromium.org>
Date: Fri Nov 16 07:12:14 2018

testing/buildbot: Use vivid for capture_unittests on ChromeOS VM in CQ

Load vivid before running capture_unittests on chromeos-amd64-generic-rel.
This makes it possible to run test cases that require a webcam.

Bug: 852302,  904730 
Change-Id: I5d4f5a1dd7a8ea27ef7eabd438fd766621573096
Signed-off-by: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/1282424
Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Takuto Ikuta <tikuta@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608688}
[modify] https://crrev.com/a81bdb917ecd5c3bd158865d35338a37ca300995/build/chromeos/run_vm_test.py
[modify] https://crrev.com/a81bdb917ecd5c3bd158865d35338a37ca300995/testing/buildbot/chromium.chromiumos.json
[modify] https://crrev.com/a81bdb917ecd5c3bd158865d35338a37ca300995/testing/buildbot/test_suites.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/b0728f91ef19cf61816f028b1a550749eb9944b6

commit b0728f91ef19cf61816f028b1a550749eb9944b6
Author: Keiichi Watanabe <keiichiw@chromium.org>
Date: Wed Nov 21 02:27:25 2018

chromeos-init: Install vivid upstart config

If USE flag 'vivid' is enabled, install vivid.conf to /etc/init/,
which loads vivid as a video capture device.

BUG= chromium:904730 ,  chromium:899595 
TEST=Made sure that /dev/video0 exists right after rebooting amd64-generic VM
TEST=Made sure that /etc/init/vivid.conf doesn't exist on kevin
TEST=tast run video.Capability on amd64-generic VM right after rebooting
TEST=tast run video.WebRTCCamera on amd64-generic VM
CQ-DEPEND=CL:1333099

Change-Id: I2a22e885af5ce98ea80fe661faa21d7e13ea1ec5
Signed-off-by: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1333102
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>

[modify] https://crrev.com/b0728f91ef19cf61816f028b1a550749eb9944b6/chromeos-base/chromeos-init/chromeos-init-9999.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/tast-tests/+/05027941ad0a7a492e332c2c62999d41215efcaf

commit 05027941ad0a7a492e332c2c62999d41215efcaf
Author: Keiichi Watanabe <keiichiw@chromium.org>
Date: Wed Nov 21 02:27:25 2018

video.WebRTC*: Don't load/unload vivid in Tast tests

Since vivid is loaded by upstart service on VM boards, each test
case doesn't have to load/unload it any more.

But, we still need to check if the device is VM or not. It's because
we check the ratio of broken frames when the used camera is vivid,
which doesn't have hardware flakiness.

BUG= chromium:904730 ,  chromium:899595 
TEST=tast run video.WebRTCCamera on amd64-generic VM
TEST=tast run video.Capability after running WebRTC tests on VM
CQ-DEPEND=CL:1333099, CL:1333102

Change-Id: I2e794a72dc1f826f887c8489a03c7a5206f1226c
Signed-off-by: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1335058
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Shuhei Takahashi <nya@chromium.org>

[modify] https://crrev.com/05027941ad0a7a492e332c2c62999d41215efcaf/src/chromiumos/tast/local/bundles/cros/video/webrtc/webrtc.go

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/cf30ae11494b102f27ffdec4d803abee6d05753f

commit cf30ae11494b102f27ffdec4d803abee6d05753f
Author: Keiichi Watanabe <keiichiw@chromium.org>
Date: Wed Nov 21 02:27:24 2018

init: Add vivid.conf

Add config file to load vivid at start-up time.

BUG= chromium:904730 ,  chromium:899595 
TEST=Made sure that vivid was loaded after rebooting amd64-generic VM
     (with CL:1333102)
Change-Id: Ice02e2d93ccb858fb1098c6ae00ea50323390be6
Signed-off-by: Keiichi Watanabe <keiichiw@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1333099
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>

[add] https://crrev.com/cf30ae11494b102f27ffdec4d803abee6d05753f/init/upstart/vivid/vivid.conf