Remove GetVolume from media::AudioRendererSink.

Remove GetVolume from media::AudioRendererSink.

This was the only method that could not be implemented in an async fashion
which is why a couple of implementations cached the volume in SetVolume
in order to implement GetVolume.  However, AudioRendererSink::GetVolume is
never used, so I think it's safe to remove it and simplify the implementations
a bit.  If/when we need it, we should have a version that supports a callback
or use the RenderCallback interface to provide the currently set volume
asynchronously.

AudioRendererMixerInput is the only class whose GetVolume method is being used
but it's not being used via the AudioRendererSink, so I simply made GetVolume
a class method and not an implementation of AudioRendererSink.

BUG=none
TEST=none


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=146731

[DaleCurtis, 2012-07-14 03:41:24]

On 2012/07/13 13:12:31, tommi wrote:

lgtm! I'm amazed among all the uses there were no unit tests using GetVolume :)

[tommi (sloooow) - chröme, 2012-07-14 07:21:48]

On 2012/07/14 03:41:24, DaleCurtis wrote:
> On 2012/07/13 13:12:31, tommi wrote:
> 
> lgtm! I'm amazed among all the uses there were no unit tests using GetVolume
:)
Thanks. Yes, we could really do with more tests

[commit-bot: I haz the power, 2012-07-14 07:22:06]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tommi@chromium.org/10703191/1

[commit-bot: I haz the power, 2012-07-14 08:24:01]

Try job failure for 10703191-1 (retry) on mac_rel for step "browser_tests".
It's a second try, previously, step "browser_tests" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...

[commit-bot: I haz the power, 2012-07-14 10:39:18]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tommi@chromium.org/10703191/1

[commit-bot: I haz the power, 2012-07-14 11:45:18]

Try job failure for 10703191-1 (retry) on mac_rel for step "browser_tests".
It's a second try, previously, step "browser_tests" failed.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...

[commit-bot: I haz the power, 2012-07-14 12:35:16]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tommi@chromium.org/10703191/1

[commit-bot: I haz the power, 2012-07-14 13:51:32]

Change committed as 146731