Adds method to invoke platform provided audio input UI.

Adds method to invoke platform provided audio input UI.
This will be used in a future CL by the speech input feature.

BUG=69886
TEST=none

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=76363

[Alpha Left Google, 2011-02-28 19:12:06]

In general AudioManager is accessed on IO thread, however the way we show the
audio input dialogs is by calling external applications, which has the problem
of blocking the IO thread or the audio thread, please add comments in
AudioManager that they should be executed on the process launcher thread.

LGTM if this is taken care of.

[Satish, 2011-02-28 19:43:20]

Thanks. As discussed I have added a comment about this and will make sure the
calling code calls these in a non-critical thread. I couldn't use process
launcher thread as is here since media has no dependency over the browser
threads.

[scherkus (not reviewing), 2011-02-28 21:18:13]

I also share concerns over launching processes...

I'm not familiar with the process launcher thread, but is it possible to have
the callee use post a task to call ShowAudioInputSettings?

if so then I think we're OK -- there's no need to introduce that dependency here
since different applications (like under media/tools) don't necessarily need to
worry about threading restrictions :)

http://codereview.chromium.org/6602012/diff/1007/media/audio/audio_manager_ba...
File media/audio/audio_manager_base.h (right):

http://codereview.chromium.org/6602012/diff/1007/media/audio/audio_manager_ba...
media/audio/audio_manager_base.h:27: virtual bool CanShowAudioInputSettings() {
return false; }
de-inline virtual methods
http://dev.chromium.org/developers/coding-style#TOC-Inline-functions

http://codereview.chromium.org/6602012/diff/1007/media/audio/linux/audio_mana...
File media/audio/linux/audio_manager_linux.cc (right):

http://codereview.chromium.org/6602012/diff/1007/media/audio/linux/audio_mana...
media/audio/linux/audio_manager_linux.cc:9: #include "base/nix/xdg_util.h"
alphabetize includes

[Satish, 2011-02-28 21:30:44]

> I'm not familiar with the process launcher thread, but is it possible to have
> the callee use post a task to call ShowAudioInputSettings?
> 
> if so then I think we're OK -- there's no need to introduce that dependency
here
> since different applications (like under media/tools) don't necessarily need
to
> worry about threading restrictions :)

Yes that is the idea, but the callee can't directly ask PostTask to invoke
ShowAudioInputSettings since this class isn't refcounted. However I can make
ShowAudioInputSettings() a static function which would simplify for the callees.
Thoughts?

[scherkus (not reviewing), 2011-02-28 21:38:48]

On 2011/02/28 21:30:44, Satish wrote:
> > I'm not familiar with the process launcher thread, but is it possible to
have
> > the callee use post a task to call ShowAudioInputSettings?
> > 
> > if so then I think we're OK -- there's no need to introduce that dependency
> here
> > since different applications (like under media/tools) don't necessarily need
> to
> > worry about threading restrictions :)
> 
> Yes that is the idea, but the callee can't directly ask PostTask to invoke
> ShowAudioInputSettings since this class isn't refcounted. However I can make
> ShowAudioInputSettings() a static function which would simplify for the
callees.
> Thoughts?

Since AudioManager is (roughly!) a singleton it might make sense to disable
ref-counting for tasks.  See base/task.h

DISABLE_RUNNABLE_METHOD_REFCOUNT(media::AudioManager);

OR we split the settings stuff into a whole separate class but that seems
overkill