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

chrome/browser/chromeos/audio/audio_mixer_alsa.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_MIXER_ALSA_H_
 #define CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_MIXER_ALSA_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 15 matching lines @@
  public:
   AudioMixerAlsa();
   virtual ~AudioMixerAlsa();
 
   // AudioMixer implementation.
   virtual void Init() OVERRIDE;
   virtual double GetVolumePercent() OVERRIDE;
   virtual void SetVolumePercent(double percent) OVERRIDE;
   virtual bool IsMuted() OVERRIDE;
   virtual void SetMuted(bool muted) OVERRIDE;
+  virtual bool IsMuteLocked() OVERRIDE;
+  virtual void SetMuteLocked(bool locked) OVERRIDE;
+  virtual bool IsCaptureMuted() OVERRIDE;
+  virtual void SetCaptureMuted(bool mute) OVERRIDE;
+  virtual bool IsCaptureMuteLocked() OVERRIDE;
+  virtual void SetCaptureMuteLocked(bool locked) OVERRIDE;
 
  private:
   // Tries to connect to ALSA.  On failure, posts a delayed Connect() task to
   // try again.
   void Connect();
 
   // Helper method called by Connect().  On success, initializes
   // |min_volume_db_|, |max_volume_db_|, |alsa_mixer_|, and |element_*| and
   // returns true.
   bool ConnectInternal();
@@ skipping 22 matching lines @@
                         double rounding_bias);
 
   // Mutes or unmutes |element|.
   void SetElementMuted(_snd_mixer_elem* element, bool mute);
 
   // Converts between percentages (in the range [0.0, 100.0]) and decibels.
   // |lock_| must be held.
   double DbToPercent(double db) const;
   double PercentToDb(double percent) const;
 
-  // Guards |min_volume_db_|, |max_volume_db_|, |volume_db_|, |is_muted_|,
+  // Guards |min_volume_db_|, |max_volume_db_|, |volume_db_|, the mute state,

[Mattias Nissler (ping if slow), 2012/08/28 12:24:24]

I'd just list the additional members for clarity.

[pastarmovj, 2012/08/28 15:11:50]

Done.

   // |apply_is_pending_|, and |initial_volume_percent_|.
   base::Lock lock_;
 
   // Volume range limits are computed once in ConnectInternal().
   double min_volume_db_;
   double max_volume_db_;
 
   // Most recently-requested volume, in decibels.  This variable is updated
   // immediately by SetVolumePercent() (post-initialization); the actual mixer
   // volume is updated later on |thread_| by ApplyState().
   double volume_db_;
 
-  // Most recently-requested muting state.
+  // Most recently-requested muting state. We don't have control over ALSA so
+  // other sound clients might unmute channels but we can do best effort to
+  // mimic CRASes locking functionality.

[Daniel Erat, 2012/08/27 17:38:35]

nit: s/CRASes/CRAS's/

[pastarmovj, 2012/08/28 15:11:50]

Done.

   bool is_muted_;
+  bool is_mute_locked_;

[Daniel Erat, 2012/08/27 17:38:35]

nit: move is_mute_locked_ and is_capture_mute_locked_ together and add a comment
describing that when they're true, the state of is_muted_ and is_capture_muted_
can't be changed

[pastarmovj, 2012/08/28 15:11:50]

Done.

+  bool is_capture_muted_;
+  bool is_capture_mute_locked_;
 
   // Is there already a pending call to ApplyState() scheduled on |thread_|?
   bool apply_is_pending_;
 
   // Before |min_volume_db_| and |max_volume_db_| are fetched from ALSA, we
   // can't convert percentages to decibels.  The default initial volume and any
   // subsequent requests we get early on are stored here and then applied during
   // initialization.  This variable is unused after initialization.
   double initial_volume_percent_;
 
   // Connection to ALSA.  NULL if not connected.
   _snd_mixer* alsa_mixer_;
 
   // Master mixer.
   _snd_mixer_elem* master_element_;
 
   // PCM mixer.  May be NULL if the driver doesn't expose one.
   _snd_mixer_elem* pcm_element_;
 
+  // Mic mixers.  Used to mute capture. Both might be NULL on some drivers.

[Mattias Nissler (ping if slow), 2012/08/28 12:24:24]

nit: Two spaces after period seems to be the rule int this file.

[pastarmovj, 2012/08/28 15:11:50]

Done.

+  _snd_mixer_elem* mic_element_;
+  _snd_mixer_elem* front_mic_element_;
+
   // Signalled after Disconnect() finishes (which is itself invoked by the
   // d'tor).
   base::WaitableEvent disconnected_event_;
 
   // Background thread used for interacting with ALSA.
   scoped_ptr<base::Thread> thread_;
 
   // Number of times that we've attempted to connect to ALSA.  Just used to keep
   // us from spamming the logs.
   int num_connection_attempts_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioMixerAlsa);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_AUDIO_AUDIO_MIXER_ALSA_H_