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

chrome/browser/chromeos/audio/audio_handler.cc

Index: chrome/browser/chromeos/audio/audio_handler.cc
diff --git a/chrome/browser/chromeos/audio/audio_handler.cc b/chrome/browser/chromeos/audio/audio_handler.cc
index 76eb60a9af31f2e8584ba5b8b559e42073439018..72233f58900739a77758457b2a0aec0b87281635 100644
--- a/chrome/browser/chromeos/audio/audio_handler.cc
+++ b/chrome/browser/chromeos/audio/audio_handler.cc
@@ -15,9 +15,13 @@
 #else
 #include "chrome/browser/chromeos/audio/audio_mixer_alsa.h"
 #endif
+#include "chrome/browser/chromeos/login/user_manager.h"
 #include "chrome/browser/prefs/pref_service.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_notification_types.h"
 #include "chrome/common/pref_names.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_service.h"
 
 using std::max;
 using std::min;
@@ -80,6 +84,14 @@ void AudioHandler::RegisterPrefs(PrefService* local_state) {
                                      kPrefMuteOff,
                                      PrefService::UNSYNCABLE_PREF);
 
+  // Register the prefs backing the audio muting policies.
+  local_state->RegisterBooleanPref(prefs::kAudioOutputEnabled,

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

i'm a bit concerned that having both kAudioOutputEnabled and kAudioMute prefs
may be confusing.  renaming kAudioOutputEnabled to something like
kAudioOutputAllowed or kAudioOutputPermitted would make the distinction between
the two clearer.

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

How strong do you feel about changing the name here. I have picked the name to
be consistent with the name of the policy and the general naming scheme we use
for such policies. I can of course change the name of the pref independent of
the policy name and will do this if you insist. However I propose instead to
extend the description of the kAudioOutputEnabled and kAudioMute policies with
the following : "This pref supersedes |kAudioMute| but does not overwrite it,
therefore when the policy is lifted the original mute state is restored." and
the reciprocal text on the other one : "This pref is ignored if
|kAudioOutputEnabled| is set to false, but its value is preserved, therefore
when the policy is lifted the original mute state is restored."

+                                  true,
+                                  PrefService::UNSYNCABLE_PREF);
+  local_state->RegisterBooleanPref(prefs::kAudioCaptureEnabled,
+                                  true,
+                                  PrefService::UNSYNCABLE_PREF);
+
   // Register the old decibel-based pref so we can clear it.
   // TODO(derat): Remove this after R20: http://crbug.com/112039
   if (!local_state->FindPreference(prefs::kAudioVolumeDb))
@@ -99,7 +111,7 @@ void AudioHandler::SetVolumePercent(double volume_percent) {
   if (IsMuted() && volume_percent > 0.0)
     SetMuted(false);
   mixer_->SetVolumePercent(volume_percent);
-  prefs_->SetDouble(prefs::kAudioVolumePercent, volume_percent);
+  local_state_->SetDouble(prefs::kAudioVolumePercent, volume_percent);
   FOR_EACH_OBSERVER(VolumeObserver, volume_observers_, OnVolumeChanged());
 }
 
@@ -112,11 +124,23 @@ bool AudioHandler::IsMuted() {
 }
 
 void AudioHandler::SetMuted(bool mute) {
-  mixer_->SetMuted(mute);
-  prefs_->SetInteger(prefs::kAudioMute, mute ? kPrefMuteOn : kPrefMuteOff);
+  if (!mixer_->IsMuteLocked()) {
+    mixer_->SetMuted(mute);
+    local_state_->SetInteger(prefs::kAudioMute,
+                             mute ? kPrefMuteOn : kPrefMuteOff);
+  }
   FOR_EACH_OBSERVER(VolumeObserver, volume_observers_, OnMuteToggled());
 }
 
+bool AudioHandler::IsCaptureMuted() {
+  return mixer_->IsCaptureMuted();
+}
+
+void AudioHandler::SetCaptureMuted(bool mute) {
+  if (!mixer_->IsCaptureMuteLocked())
+    mixer_->SetCaptureMuted(mute);
+}
+
 void AudioHandler::AddVolumeObserver(VolumeObserver* observer) {
   volume_observers_.AddObserver(observer);
 }
@@ -125,11 +149,26 @@ void AudioHandler::RemoveVolumeObserver(VolumeObserver* observer) {
   volume_observers_.RemoveObserver(observer);
 }
 
+void AudioHandler::Observe(int type,
+                           const content::NotificationSource& source,
+                           const content::NotificationDetails& details) {
+  if (type == chrome::NOTIFICATION_PREF_CHANGED) {
+    std::string* pref_name = content::Details<std::string>(details).ptr();
+    if (*pref_name == prefs::kAudioOutputEnabled ||
+        *pref_name == prefs::kAudioCaptureEnabled) {
+      ApplyAudioPolicy();
+    }
+  } else {
+    NOTREACHED();

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

nit: NOTREACHED() << "Unexpected notification " << type;

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

Done.

+  }
+}
+
 AudioHandler::AudioHandler(AudioMixer* mixer)
     : mixer_(mixer),
-      prefs_(g_browser_process->local_state()) {
-  mixer_->SetVolumePercent(prefs_->GetDouble(prefs::kAudioVolumePercent));
-  mixer_->SetMuted(prefs_->GetInteger(prefs::kAudioMute) == kPrefMuteOn);
+      local_state_(g_browser_process->local_state()) {
+  InitializePrefObservers();
+  ApplyAudioPolicy();
+  mixer_->SetVolumePercent(local_state_->GetDouble(prefs::kAudioVolumePercent));
   mixer_->Init();
 }
 
@@ -137,4 +176,30 @@ AudioHandler::~AudioHandler() {
   mixer_.reset();
 };
 
+void AudioHandler::InitializePrefObservers() {
+  pref_change_registrar_.Init(local_state_);
+  pref_change_registrar_.Add(prefs::kAudioOutputEnabled, this);
+  pref_change_registrar_.Add(prefs::kAudioCaptureEnabled, this);
+}
+
+void AudioHandler::ApplyAudioPolicy() {
+  if (local_state_->GetBoolean(prefs::kAudioOutputEnabled)) {
+    mixer_->SetMuteLocked(false);
+    mixer_->SetMuted(
+        local_state_->GetInteger(prefs::kAudioMute) == kPrefMuteOn);
+  } else {
+    mixer_->SetMuted(true);
+    mixer_->SetMuteLocked(true);
+  }
+  FOR_EACH_OBSERVER(VolumeObserver, volume_observers_, OnMuteToggled());
+  if (local_state_->GetBoolean(prefs::kAudioCaptureEnabled)) {
+    mixer_->SetCaptureMuteLocked(false);
+    mixer_->SetCaptureMuted(false);
+  } else {
+    mixer_->SetCaptureMuted(true);
+    mixer_->SetCaptureMuteLocked(true);
+  }
+}
+
+
 }  // namespace chromeos