gpu: Introduce GpuChannelEstablishFactory.

gpu: Introduce GpuChannelEstablishFactory.

This CL introduces GpuChannelEstablishFactory, which can be used to make a
connection to the GPU process. For mus, the ui::GpuService installs itself
as the factory. With this approach, less code in content/ needs to know
about mus. If no factory is installed, then BrowserGpuChannelHostFactory is
used instead.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:closure_compilation

Committed: https://crrev.com/3f6627d640a0badc8185c96ad19095116d1569e3
Cr-Commit-Position: refs/heads/master@{#410612}

[sadrul, 2016-07-29 16:24:02]

Description was changed from

==========
[wip] Several changes related to gpu code.

. Have an explicit lifetime/ownership of ui::GpuService
. Include the established channel in the EstablishGpuChannel() reply callback in
  GpuService and BrowserGpuChannelHostFactory.

BUG=none
==========

to

==========
[wip] Several changes related to gpu code.

. Have an explicit lifetime/ownership of ui::GpuService
. Include the established channel in the EstablishGpuChannel() reply callback in
  GpuService and BrowserGpuChannelHostFactory.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
==========

[sadrul, 2016-07-29 16:24:10]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-29 16:24:46]

Dry run: 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, 2016-07-29 16:26:38]

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

[commit-bot: I haz the power, 2016-07-29 16:26:39]

Dry run: Try jobs failed on following builders:
  ios-device on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device/builds...)
  ios-device-gn on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-device-gn/bui...)
  ios-simulator on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator/bui...)
  ios-simulator-gn on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios-simulator-gn/...)

[sadrul, 2016-07-29 16:37:23]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-29 16:37:55]

Dry run: 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, 2016-07-29 17:04:01]

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

[commit-bot: I haz the power, 2016-07-29 17:04:02]

Dry run: Try jobs failed on following builders:
  cast_shell_android on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/cast_shell_a...)
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)

[sadrul, 2016-07-29 18:31:55]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-29 18:32:32]

Dry run: 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, 2016-07-29 19:23:15]

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

[commit-bot: I haz the power, 2016-07-29 19:23:16]

Dry run: Try jobs failed on following builders:
  mac_optional_gpu_tests_rel on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_optional_gpu_...)

[sadrul, 2016-07-29 20:11:24]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-29 20:11:46]

Dry run: 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, 2016-07-29 20:57:37]

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

[commit-bot: I haz the power, 2016-07-29 20:57:38]

Dry run: This issue passed the CQ dry run.

[sadrul, 2016-07-29 23:23:31]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-29 23:23:57]

Dry run: 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, 2016-07-30 00:15:15]

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

[commit-bot: I haz the power, 2016-07-30 00:15:16]

Dry run: This issue passed the CQ dry run.

[sadrul, 2016-07-30 00:50:35]

Description was changed from

==========
[wip] Several changes related to gpu code.

. Have an explicit lifetime/ownership of ui::GpuService
. Include the established channel in the EstablishGpuChannel() reply callback in
  GpuService and BrowserGpuChannelHostFactory.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
==========

to

==========
gpu: Introduce GpuChannelEstablishFactory.

This CL introduces GpuChannelEstablishFactory, which can be used to make a
connection to the GPU process. For mus, the ui::GpuService installs itself
as the factory. With this approach, less code in content/ needs to know
about mus. If no factory is installed, then BrowserGpuChannelHostFactory is
used instead.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
==========

[sadrul, 2016-07-30 01:06:49]

sadrul@chromium.org changed reviewers:
+ piman@chromium.org

[sadrul, 2016-07-30 01:06:50]

I considered making BrowserGpuChannelHostFactory into a
GpuChannelEstablishFactory too. I think that would've been nice. But to do that,
CauseForGpuLaunch will need to move into gpu/ out of content/common. Do you
think that'd be OK?

On a sidenote: I feel like GpuChannelHostDelegate would be a better name for
what is currently called GpuChannelHostFactory. (and GpuChannelHostFactory would
be a better name for what this CL calls GpuChannelEstablishFactory)

[sadrul, 2016-07-30 01:10:13]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-07-30 01:10:32]

Dry run: 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, 2016-07-30 03:14:11]

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

[commit-bot: I haz the power, 2016-07-30 03:14:11]

Dry run: Try jobs failed on following builders:
  mac_optional_gpu_tests_rel on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_optional_gpu_...)

[piman, 2016-08-02 03:14:45]

CauseForGpuLaunch doesn't fit well in gpu/ because it encodes concerns of the
higher levels.

That said, I think we don't really need it any more - it's essentially only used
to report in UMA, to track what would cause it to launch - but nowadays, we
always launch it at startup anyway (or not at all), so the enum is moot, so I
would be ok with just removing it.

re: names, agreed that GpuChannelHostFactory could be renamed
GpuChannelHostDelegate (it used to have the EstablishGpuChannel, but that was
moved out to the call sites).

https://codereview.chromium.org/2197613003/diff/100001/gpu/ipc/client/gpu_cha...
File gpu/ipc/client/gpu_channel_host.cc (right):

https://codereview.chromium.org/2197613003/diff/100001/gpu/ipc/client/gpu_cha...
gpu/ipc/client/gpu_channel_host.cc:30: GpuChannelEstablishFactory*
g_creator_factory = nullptr;
I would like to avoid globals in GPU code. This breaks for e.g. single process
mode.
Can we instead inject the Factory where it's needed?

[sadrul, 2016-08-03 17:56:02]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-03 17:56:49]

Dry run: 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, 2016-08-03 18:34:03]

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

[commit-bot: I haz the power, 2016-08-03 18:34:03]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)

[sadrul, 2016-08-04 03:43:12]

sadrul@chromium.org changed reviewers:
- piman@chromium.org

[sadrul, 2016-08-04 17:27:43]

Description was changed from

==========
gpu: Introduce GpuChannelEstablishFactory.

This CL introduces GpuChannelEstablishFactory, which can be used to make a
connection to the GPU process. For mus, the ui::GpuService installs itself
as the factory. With this approach, less code in content/ needs to know
about mus. If no factory is installed, then BrowserGpuChannelHostFactory is
used instead.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
==========

to

==========
gpu: Introduce GpuChannelEstablishFactory.

This CL introduces GpuChannelEstablishFactory, which can be used to make a
connection to the GPU process. For mus, the ui::GpuService installs itself
as the factory. With this approach, less code in content/ needs to know
about mus. If no factory is installed, then BrowserGpuChannelHostFactory is
used instead.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:closure_compilation
==========

[sadrul, 2016-08-04 17:28:39]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-04 17:29:09]

Dry run: 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, 2016-08-04 17:44:27]

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

[commit-bot: I haz the power, 2016-08-04 17:44:31]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)

[sadrul, 2016-08-04 19:40:05]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-04 19:40:54]

Dry run: 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, 2016-08-04 19:54:39]

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

[commit-bot: I haz the power, 2016-08-04 19:54:40]

Dry run: Try jobs failed on following builders:
  android_compile_dbg on master.tryserver.chromium.android (JOB_FAILED,
https://build.chromium.org/p/tryserver.chromium.android/builders/android_comp...)

[sadrul, 2016-08-05 04:21:55]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-05 04:22:13]

Dry run: 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, 2016-08-05 04:39:45]

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

[commit-bot: I haz the power, 2016-08-05 04:39:46]

Dry run: Try jobs failed on following builders:
  cast_shell_linux on master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/cast_shell_linu...)

[sadrul, 2016-08-05 05:13:19]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-05 05:13:35]

Dry run: 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, 2016-08-05 05:44:12]

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

[commit-bot: I haz the power, 2016-08-05 05:44:13]

Dry run: Try jobs failed on following builders:
  mac_chromium_compile_dbg_ng on master.tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)

[sadrul, 2016-08-05 05:48:36]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-05 05:48:58]

Dry run: 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, 2016-08-05 06:12:38]

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

[commit-bot: I haz the power, 2016-08-05 06:12:39]

Dry run: Try jobs failed on following builders:
  linux_chromium_chromeos_ozone_rel_ng on master.tryserver.chromium.linux
(JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_...)
  win_optional_gpu_tests_rel on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_optional_gpu_...)

[sadrul, 2016-08-05 06:55:38]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-05 06:55:51]

Dry run: 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, 2016-08-05 08:04:19]

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

[commit-bot: I haz the power, 2016-08-05 08:04:20]

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

[sadrul, 2016-08-05 18:21:03]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-05 18:21:27]

Dry run: 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, 2016-08-05 19:39:00]

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

[commit-bot: I haz the power, 2016-08-05 19:39:01]

Dry run: This issue passed the CQ dry run.

[sadrul, 2016-08-05 19:54:43]

sadrul@chromium.org changed reviewers:
+ piman@chromium.org

[sadrul, 2016-08-05 19:54:44]

I had to do some cleanups first (https://codereview.chromium.org/2194003002/,
https://codereview.chromium.org/2208613002/). One more
(https://codereview.chromium.org/2215353004/) remains to land, but I think this
is ready for review again. PTAL. Thanks

[sadrul, 2016-08-05 19:54:56]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-05 19:55:26]

Dry run: 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, 2016-08-05 21:42:19]

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

[commit-bot: I haz the power, 2016-08-05 21:42:20]

Dry run: This issue passed the CQ dry run.

[piman, 2016-08-08 15:36:31]

lgtm

https://codereview.chromium.org/2197613003/diff/320001/content/browser/browse...
File content/browser/browser_main_loop.cc (right):

https://codereview.chromium.org/2197613003/diff/320001/content/browser/browse...
content/browser/browser_main_loop.cc:1214:
BrowserGpuChannelHostFactory::Initialize(established_gpu_channel);
Should we avoid doing this if we use the ContentClient's factory?

[sadrul, 2016-08-08 16:25:32]

https://codereview.chromium.org/2197613003/diff/320001/content/browser/browse...
File content/browser/browser_main_loop.cc (right):

https://codereview.chromium.org/2197613003/diff/320001/content/browser/browse...
content/browser/browser_main_loop.cc:1214:
BrowserGpuChannelHostFactory::Initialize(established_gpu_channel);
On 2016/08/08 15:36:30, piman - slow reviews until 8-8 wrote:
> Should we avoid doing this if we use the ContentClient's factory?

I initially did this, but BrowserGpuChannelHostFactory initailizes
BrowserGpuMemoryBufferManager (which is currently also a singleton used in a few
places). I plan to remove its usage, and instead inject the
gpu::GpuMemoryBufferManager to use instead. But I would like to do that in a
separate CL if that sounds OK? Once that happens, we won't need to initialize
BrowserGpuChannelHostFactory at all.

[sadrul, 2016-08-08 16:34:36]

sadrul@chromium.org changed reviewers:
+ ben@chromium.org, jam@chromium.org

[sadrul, 2016-08-08 16:34:38]

+ben@chromium.org for changes in services/ui

+jam@chromium.org for changes in content/public

Note that this CL depends on https://codereview.chromium.org/2215353004/ or
https://codereview.chromium.org/2218843003/. Either way, the code in this CL
doesn't have to change (other than trivially).

[piman, 2016-08-08 18:08:33]

On Mon, Aug 8, 2016 at 9:25 AM, <sadrul@chromium.org> wrote:

>
> https://codereview.chromium.org/2197613003/diff/320001/
> content/browser/browser_main_loop.cc
> File content/browser/browser_main_loop.cc (right):
>
> https://codereview.chromium.org/2197613003/diff/320001/
> content/browser/browser_main_loop.cc#newcode1214
> content/browser/browser_main_loop.cc:1214:
> BrowserGpuChannelHostFactory::Initialize(established_gpu_channel);
> On 2016/08/08 15:36:30, piman - slow reviews until 8-8 wrote:
> > Should we avoid doing this if we use the ContentClient's factory?
>
> I initially did this, but BrowserGpuChannelHostFactory initailizes
> BrowserGpuMemoryBufferManager (which is currently also a singleton used
> in a few places). I plan to remove its usage, and instead inject the
> gpu::GpuMemoryBufferManager to use instead. But I would like to do that
> in a separate CL if that sounds OK? Once that happens, we won't need to
> initialize BrowserGpuChannelHostFactory at all.
>

SG, thanks.


>
> https://codereview.chromium.org/2197613003/
>

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[sadrul, 2016-08-08 19:07:29]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-08 19:08:05]

Dry run: 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, 2016-08-08 20:04:05]

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

[commit-bot: I haz the power, 2016-08-08 20:04:06]

Dry run: This issue passed the CQ dry run.

[Ben Goodger (Google), 2016-08-08 20:09:14]

rs lgtm for ui service stuff

[jam, 2016-08-09 01:40:35]

On 2016/08/08 16:34:38, sadrul wrote:
> mailto:+ben@chromium.org for changes in services/ui
> 
> mailto:+jam@chromium.org for changes in content/public

lgtm

[sadrul, 2016-08-09 02:41:03]

The CQ bit was checked by sadrul@chromium.org

[commit-bot: I haz the power, 2016-08-09 02:41:42]

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, 2016-08-09 02:47:54]

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

[commit-bot: I haz the power, 2016-08-09 02:47:56]

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

[sadrul, 2016-08-09 03:26:04]

The CQ bit was checked by sadrul@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-09 03:26:31]

Dry run: 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, 2016-08-09 06:05:59]

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

[commit-bot: I haz the power, 2016-08-09 06:06:01]

Dry run: Try jobs failed on following builders:
  win_chromium_rel_ng on master.tryserver.chromium.win (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.win/builders/win_chromium_rel_...)

[sadrul, 2016-08-09 07:07:32]

The CQ bit was checked by sadrul@chromium.org

[sadrul, 2016-08-09 07:07:33]

The patchset sent to the CQ was uploaded after l-g-t-m from jam@chromium.org,
ben@chromium.org, piman@chromium.org
Link to the patchset: https://codereview.chromium.org/2197613003/#ps340001
(title: "tot merge")

[commit-bot: I haz the power, 2016-08-09 07:08:10]

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, 2016-08-09 08:11:55]

Committed patchset #18 (id:340001)

[commit-bot: I haz the power, 2016-08-09 08:14:22]

Description was changed from

==========
gpu: Introduce GpuChannelEstablishFactory.

This CL introduces GpuChannelEstablishFactory, which can be used to make a
connection to the GPU process. For mus, the ui::GpuService installs itself
as the factory. With this approach, less code in content/ needs to know
about mus. If no factory is installed, then BrowserGpuChannelHostFactory is
used instead.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:closure_compilation
==========

to

==========
gpu: Introduce GpuChannelEstablishFactory.

This CL introduces GpuChannelEstablishFactory, which can be used to make a
connection to the GPU process. For mus, the ui::GpuService installs itself
as the factory. With this approach, less code in content/ needs to know
about mus. If no factory is installed, then BrowserGpuChannelHostFactory is
used instead.

BUG=none
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:closure_compilation

Committed: https://crrev.com/3f6627d640a0badc8185c96ad19095116d1569e3
Cr-Commit-Position: refs/heads/master@{#410612}
==========

[commit-bot: I haz the power, 2016-08-09 08:14:24]

Patchset 18 (id:??) landed as
https://crrev.com/3f6627d640a0badc8185c96ad19095116d1569e3
Cr-Commit-Position: refs/heads/master@{#410612}