Implement two new policies to control muting the audio I/O.

chrome/browser/chromeos/audio/audio_mixer.h

Index: chrome/browser/chromeos/audio/audio_mixer.h
diff --git a/chrome/browser/chromeos/audio/audio_mixer.h b/chrome/browser/chromeos/audio/audio_mixer.h
index cb9dd67d951fbdb144392b99fdea37a3508220d0..b184e55b7697360b4a82b0a0d5cd21675633d33b 100644
--- a/chrome/browser/chromeos/audio/audio_mixer.h
+++ b/chrome/browser/chromeos/audio/audio_mixer.h
@@ -26,12 +26,36 @@ class AudioMixer {
   // |percent| should be in the range [0.0, 100.0].
   virtual void SetVolumePercent(double percent) = 0;
 
-  // Is the device currently muted?
+  // Is the device currently muted?  If SetMuteLocked has been called with true
+  // this function will not change the mute state until it is unlocked with

[Daniel Erat, 2012/08/29 15:37:00]

is this comment meant to be above SetMuted() instead?  i wouldn't expect
IsMuted() to change the mute state.

[pastarmovj, 2012/08/29 16:15:52]

Shoot! Sorry, it is of course.

+  // another call to SetMuteLocked(false).
   virtual bool IsMuted() = 0;
 
-  // Mutes or unmutes the device, possibly asynchronously.
+  // Mutes or unmutes the device, possibly asynchronously.  The called must

[Daniel Erat, 2012/08/29 15:37:00]

nit: s/called/caller/

[pastarmovj, 2012/08/29 16:15:52]

Done.

+  // first verify that the mute state is not locked by calling IsMuteLocked.
   virtual void SetMuted(bool mute) = 0;
 
+  // Is the device's mute state currently locked?
+  virtual bool IsMuteLocked() = 0;
+
+  // Locks the mute state of the device to muted.  After this is done SetMute

[Daniel Erat, 2012/08/29 15:37:00]

the "to muted" bit seems inaccurate.  this method doesn't appear to lock the
state to muted in either implementation; rather, it just locks it in its current
(either muted or unmuted) state.  i'm not sure whether it'd be better to make
the comment match the code or to make the code match the comment.

[pastarmovj, 2012/08/29 16:15:52]

I would prefer to fix the comment to match the code as this also matches the
CRAS server behavior and this seems to be more future-proof without loosing the
clearness of the API.

+  // will ignore unmuting requests until SetMuteLocked is called with false.
+  virtual void SetMuteLocked(bool locked) = 0;
+
+  // Is the capture device currently muted?
+  virtual bool IsCaptureMuted() = 0;
+
+  // Mutes or unmutes the capture device, possible asynchronously.  The called

[Daniel Erat, 2012/08/29 15:37:00]

nit: s/called/caller/

[pastarmovj, 2012/08/29 16:15:52]

Done.

+  // must first verify that the mute state is not locked by calling
+  // IsCaptureMuteLocked.
+  virtual void SetCaptureMuted(bool mute) = 0;
+
+  // Is the capture device's mute state currently locked?
+  virtual bool IsCaptureMuteLocked() = 0;
+
+  // Locks the capture mute state of the device.
+  virtual void SetCaptureMuteLocked(bool locked) = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(AudioMixer);
 };