Handful of changes to get mus to shutdown correctly

Handful of changes to get mus to shutdown correctly

As part of https://codereview.chromium.org/1819063002/ we're trying to
make mus shutdown cleanly (it currently does an exit). There are a
handful of places causing problems:
. GpuState::control_task_runner() could try to get the task runner
  from the thread after the thread has been shutdown, which results in
  trying to use a null value. By caching the TaskRunner we ensure you
  can't get null.
. GpuState needs to shutdown the driver_manager_ on the gpu thread
  (driver_manager_ isn't thread safe).
. Had to add a couple of checks for the MessageLoop as it may no
  longer be around.
. Made the WindowServer be destroyed before stopping GpuThreads. If we
  don't destroy in this order StopThreads never completes.
. Made PlatfromDisplay not notify delegate from destructor.

BUG=none
TEST=covered by tests
R=fsamuel@chromium.org

Committed: https://crrev.com/571d9ef9a6b91d606dcf00d493b22f32f96ffa45
Cr-Commit-Position: refs/heads/master@{#382645}

[Fady Samuel, 2016-03-22 17:27:14]

lgtm

[sky, 2016-03-22 17:28:00]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2016-03-22 17:28:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1827453002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1827453002/1

[commit-bot: I haz the power, 2016-03-22 19:39:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-22 19:41:09]

Description was changed from

==========
Handful of changes to get mus to shutdown correctly

As part of https://codereview.chromium.org/1819063002/ we're trying to
make mus shutdown cleanly (it currently does an exit). There are a
handful of places causing problems:
. GpuState::control_task_runner() could try to get the task runner
  from the thread after the thread has been shutdown, which results in
  trying to use a null value. By caching the TaskRunner we ensure you
  can't get null.
. GpuState needs to shutdown the driver_manager_ on the gpu thread
  (driver_manager_ isn't thread safe).
. Had to add a couple of checks for the MessageLoop as it may no
  longer be around.
. Made the WindowServer be destroyed before stopping GpuThreads. If we
  don't destroy in this order StopThreads never completes.
. Made PlatfromDisplay not notify delegate from destructor.

BUG=none
TEST=covered by tests
R=fsamuel@chromium.org
==========

to

==========
Handful of changes to get mus to shutdown correctly

As part of https://codereview.chromium.org/1819063002/ we're trying to
make mus shutdown cleanly (it currently does an exit). There are a
handful of places causing problems:
. GpuState::control_task_runner() could try to get the task runner
  from the thread after the thread has been shutdown, which results in
  trying to use a null value. By caching the TaskRunner we ensure you
  can't get null.
. GpuState needs to shutdown the driver_manager_ on the gpu thread
  (driver_manager_ isn't thread safe).
. Had to add a couple of checks for the MessageLoop as it may no
  longer be around.
. Made the WindowServer be destroyed before stopping GpuThreads. If we
  don't destroy in this order StopThreads never completes.
. Made PlatfromDisplay not notify delegate from destructor.

BUG=none
TEST=covered by tests
R=fsamuel@chromium.org

Committed: https://crrev.com/571d9ef9a6b91d606dcf00d493b22f32f96ffa45
Cr-Commit-Position: refs/heads/master@{#382645}
==========

[commit-bot: I haz the power, 2016-03-22 19:41:10]

Patchset 1 (id:??) landed as
https://crrev.com/571d9ef9a6b91d606dcf00d493b22f32f96ffa45
Cr-Commit-Position: refs/heads/master@{#382645}