Revert of chromeos: Makes mushrome use simplified display management

Revert of chromeos: Makes mushrome use simplified display management (patchset #8 id:140001 of https://codereview.chromium.org/2840043003/ )

Reason for revert:
This appears to have broken https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Ozone%20Tests%20%281%29/builds/46388, and that bot has mus_browser_test failing reliably since then.

More info on the associated bug:
BUG=717523
Original issue's description:
> chromeos: Makes mushrome use simplified display management
> 
> This also adds a stanalone_ash target that is the equivalent of
> ash_shell_with_content but running in mushrome mode and without
> content.
> 
> BUG=708287, 706589
> TEST=covered by tests
> R=kylechar@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2840043003
> Cr-Commit-Position: refs/heads/master@{#468123}
> Committed: https://chromium.googlesource.com/chromium/src/+/cfaad89ae8da7b8a0d0055db9f5bc5ac76cf6cf5

TBR=kylechar@chromium.org,sky@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=708287, 706589

[vabr (Chromium), 2017-05-02 13:38:36]

The CQ bit was checked by vabr@chromium.org

[vabr (Chromium), 2017-05-02 13:38:36]

Created Revert of chromeos: Makes mushrome use simplified display management

[commit-bot: I haz the power, 2017-05-02 13:38:50]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-02 13:41:48]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-05-02 13:41:49]

Try jobs failed on following builders:
  linux_chromium_tsan_rel_ng on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)

[vabr (Chromium), 2017-05-03 07:07:38]

Description was changed from

==========
Revert of chromeos: Makes mushrome use simplified display management (patchset
#8 id:140001 of https://codereview.chromium.org/2840043003/ )

Reason for revert:
This appears to have broken
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%...,
and that bot has mus_browser_test failing reliably since then.

More info on the associated bug:
BUG=717523

Original issue's description:
> chromeos: Makes mushrome use simplified display management
> 
> This also adds a stanalone_ash target that is the equivalent of
> ash_shell_with_content but running in mushrome mode and without
> content.
> 
> BUG=708287,706589
> TEST=covered by tests
> R=kylechar@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2840043003
> Cr-Commit-Position: refs/heads/master@{#468123}
> Committed:
https://chromium.googlesource.com/chromium/src/+/cfaad89ae8da7b8a0d0055db9f5b...

TBR=kylechar@chromium.org,sky@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=708287,706589
==========

to

==========
Revert of chromeos: Makes mushrome use simplified display management (patchset
#8 id:140001 of https://codereview.chromium.org/2840043003/ )

Reason for revert:
This appears to have broken
https://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%...,
and that bot has mus_browser_test failing reliably since then.

More info on the associated bug:
BUG=717523

Original issue's description:
> chromeos: Makes mushrome use simplified display management
> 
> This also adds a stanalone_ash target that is the equivalent of
> ash_shell_with_content but running in mushrome mode and without
> content.
> 
> BUG=708287,706589
> TEST=covered by tests
> R=kylechar@chromium.org
> 
> Review-Url: https://codereview.chromium.org/2840043003
> Cr-Commit-Position: refs/heads/master@{#468123}
> Committed:
https://chromium.googlesource.com/chromium/src/+/cfaad89ae8da7b8a0d0055db9f5b...

TBR=kylechar@chromium.org,sky@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=708287,706589
==========