Bug 1113086 - AudioChannel policy in Browser API - patch 4 - Muted by default, e=alwu

dom/audiochannel/AudioChannelService.cpp

@@ -40,6 +40,9 @@ using namespace mozilla::hal;
 
 namespace {
 
+// If true, any new AudioChannelAgent will be muted when created.
+bool sAudioChannelMutedByDefault = false;
+
 void
 NotifyChannelActive(uint64_t aWindowID, AudioChannel aAudioChannel,
                     bool aActive)
@@ -169,6 +172,9 @@ AudioChannelService::AudioChannelService()
 #endif
     }
   }
+
+  Preferences::AddBoolVarCache(&sAudioChannelMutedByDefault,
+                               "dom.audiochannel.mutedByDefault");
 }
 
 AudioChannelService::~AudioChannelService()
@@ -825,6 +831,12 @@ AudioChannelService::ChildStatusReceived(uint64_t aChildID,
   data->mActiveContentOrNormalChannel = aContentOrNormalChannel;
 }
 
+/* static */ bool
+AudioChannelService::IsAudioChannelMutedByDefault()
+{
+  return sAudioChannelMutedByDefault;
+}
+
 /* static */ PLDHashOperator
 AudioChannelService::NotifyEnumerator(AudioChannelAgent* aAgent,
                                       AudioChannel* aAudioChannel,

dom/audiochannel/AudioChannelService.h

@@ -48,6 +48,8 @@ public:
    */
   static void Shutdown();
 
+  static bool IsAudioChannelMutedByDefault();
+
   /**
    * Any audio channel agent that starts playing should register itself to
    * this service, sharing the AudioChannel.
@@ -146,7 +148,7 @@ private:
   {
     AudioChannelConfig()
       : mVolume(1.0)
-      , mMuted(false)
+      , mMuted(IsAudioChannelMutedByDefault())
       , mNumberOfAgents(0)
     {}
 

modules/libpref/init/all.js

@@ -4954,6 +4954,8 @@ pref("reader.toolbar.vertical", true);
 pref("media.gmp.insecure.allow", false);
 #endif
 
+pref("dom.audiochannel.mutedByDefault", false);
+
 // Use vsync aligned rendering. b2g prefs are in b2g.js.
 // Hardware vsync supported on windows, os x, and b2g.
 // Linux and fennec will use software vsync.