Add support for real audio output to mojo.

Add support for real audio output to mojo.

This isn't what we want to do long term, but it allows audio playback
for now. It's just an adapter between the browser side AudioOutputStream
and the renderer side AudioRendererSink.

Note this will not work if html_viewer is sandboxed, which is why we
need to come up with a generic audio output service next.

BUG=none
TEST=mojo demo launcher

Committed: https://crrev.com/b8792792795dd2c1956fcce4e93d1a7e46fb2218
Cr-Commit-Position: refs/heads/master@{#300794}

[DaleCurtis, 2014-10-21 00:11:02]

Patchset #1 (id:1) has been deleted

[DaleCurtis, 2014-10-21 00:13:13]

dalecurtis@chromium.org changed reviewers:
+ jamesr@chromium.org, xhwang@chromium.org

[DaleCurtis, 2014-10-21 00:13:42]

Based on email discussions, we'll go ahead and land this. Please review.

[jamesr, 2014-10-21 00:15:45]

mojo/ lgtm

https://codereview.chromium.org/651373003/diff/20001/mojo/services/html_viewe...
File mojo/services/html_viewer/webmediaplayer_factory.cc (right):

https://codereview.chromium.org/651373003/diff/20001/mojo/services/html_viewe...
mojo/services/html_viewer/webmediaplayer_factory.cc:74: // TODO(dalecurtis):
Replace this with an interface to an actual mojo service;
can you tie this to a crbug that describes the issue and where people can track
progress?

[DaleCurtis, 2014-10-21 00:23:32]

https://codereview.chromium.org/651373003/diff/20001/mojo/services/html_viewe...
File mojo/services/html_viewer/webmediaplayer_factory.cc (right):

https://codereview.chromium.org/651373003/diff/20001/mojo/services/html_viewe...
mojo/services/html_viewer/webmediaplayer_factory.cc:74: // TODO(dalecurtis):
Replace this with an interface to an actual mojo service;
On 2014/10/21 00:15:45, jamesr wrote:
> can you tie this to a crbug that describes the issue and where people can
track
> progress?

Done.

[xhwang, 2014-10-22 16:31:53]

lgtm % nits

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
File media/audio/audio_output_stream_sink.h (right):

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
media/audio/audio_output_stream_sink.h:36: virtual bool SetVolume(double volume)
override;
s/virtual//

Basically only use one of {virtual, override, final}:

https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/VTNZzizN0zo

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
media/audio/audio_output_stream_sink.h:40: virtual void
OnError(AudioOutputStream* stream) override;
ditto

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
media/audio/audio_output_stream_sink.h:57: // Parameters provided by
Initialize(), cached for use on other threads.
Can you explain the threading model of this class? We have an audio thread and a
lock, but it's not clear how this these work together.

[DaleCurtis, 2014-10-22 21:33:44]

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
File media/audio/audio_output_stream_sink.h (right):

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
media/audio/audio_output_stream_sink.h:36: virtual bool SetVolume(double volume)
override;
On 2014/10/22 16:31:53, xhwang wrote:
> s/virtual//
> 
> Basically only use one of {virtual, override, final}:
> 
>
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/VTNZzizN0zo

Done.

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
media/audio/audio_output_stream_sink.h:40: virtual void
OnError(AudioOutputStream* stream) override;
On 2014/10/22 16:31:53, xhwang wrote:
> ditto

Done.

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
media/audio/audio_output_stream_sink.h:57: // Parameters provided by
Initialize(), cached for use on other threads.
On 2014/10/22 16:31:53, xhwang wrote:
> Can you explain the threading model of this class? We have an audio thread and
a
> lock, but it's not clear how this these work together.

The threading model is explained here:
https://code.google.com/p/chromium/codesearch#chromium/src/media/audio/audio_...

I can elaborate some more here if you like, but we haven't typically added such
comments to the implementors of that interface.

[xhwang, 2014-10-22 21:37:31]

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
File media/audio/audio_output_stream_sink.h (right):

https://codereview.chromium.org/651373003/diff/40001/media/audio/audio_output...
media/audio/audio_output_stream_sink.h:57: // Parameters provided by
Initialize(), cached for use on other threads.
On 2014/10/22 21:33:44, DaleCurtis wrote:
> On 2014/10/22 16:31:53, xhwang wrote:
> > Can you explain the threading model of this class? We have an audio thread
and
> a
> > lock, but it's not clear how this these work together.
> 
> The threading model is explained here:
>
https://code.google.com/p/chromium/codesearch#chromium/src/media/audio/audio_...
> 
> I can elaborate some more here if you like, but we haven't typically added
such
> comments to the implementors of that interface.

I didn't know that. Thanks! Agreed that we don't need to duplicate the docs
here.

[DaleCurtis, 2014-10-22 21:40:20]

The CQ bit was checked by dalecurtis@chromium.org

[commit-bot: I haz the power, 2014-10-22 21:41:20]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/651373003/60001

[commit-bot: I haz the power, 2014-10-22 23:33:42]

Committed patchset #3 (id:60001)

[commit-bot: I haz the power, 2014-10-22 23:35:37]

Patchset 3 (id:??) landed as
https://crrev.com/b8792792795dd2c1956fcce4e93d1a7e46fb2218
Cr-Commit-Position: refs/heads/master@{#300794}