Add a method to tab_utils.h to find out whether a tab is playing audio.

content/browser/renderer_host/media/audio_renderer_host.cc

Index: content/browser/renderer_host/media/audio_renderer_host.cc
diff --git a/content/browser/renderer_host/media/audio_renderer_host.cc b/content/browser/renderer_host/media/audio_renderer_host.cc
index 83b5f2510baaa405905af5e07c561e76283b9ade..3453cd90ffd2ad494e919377fd29b565048cbaaf 100644
--- a/content/browser/renderer_host/media/audio_renderer_host.cc
+++ b/content/browser/renderer_host/media/audio_renderer_host.cc
@@ -39,11 +39,14 @@ struct AudioRendererHost::AudioEntry {
 
   // Set to true after we called Close() for the controller.
   bool pending_close;
+
+  int render_view_id;
 };
 
 AudioRendererHost::AudioEntry::AudioEntry()
     : stream_id(0),
-      pending_close(false) {
+      pending_close(false),
+      render_view_id(0) {

[miu, 2012/12/19 00:49:08]

nit: This should probably default to MSG_ROUTING_NONE instead of 0.

 }
 
 AudioRendererHost::AudioEntry::~AudioEntry() {}
@@ -51,8 +54,11 @@ AudioRendererHost::AudioEntry::~AudioEntry() {}
 ///////////////////////////////////////////////////////////////////////////////
 // AudioRendererHost implementations.
 AudioRendererHost::AudioRendererHost(
-    media::AudioManager* audio_manager, MediaObserver* media_observer)
-    : audio_manager_(audio_manager),
+    int render_process_id,
+    media::AudioManager* audio_manager,
+    MediaObserver* media_observer)
+    : render_process_id_(render_process_id),
+      audio_manager_(audio_manager),
       media_observer_(media_observer) {
 }
 
@@ -285,10 +291,15 @@ void AudioRendererHost::OnCreateStream(
 
 void AudioRendererHost::OnAssociateStreamWithProducer(int stream_id,
                                                       int render_view_id) {
-  // TODO(miu): Will use render_view_id in upcoming change.
-  DVLOG(1) << "AudioRendererHost@" << this
-           << "::OnAssociateStreamWithProducer(stream_id=" << stream_id
-           << ", render_view_id=" << render_view_id << ")";
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+
+  AudioEntry* entry = LookupById(stream_id);
+  if (!entry) {
+    SendErrorMessage(stream_id);
+    return;
+  }
+
+  entry->render_view_id = render_view_id;

[miu, 2012/12/19 00:49:08]

While you're here, could you add a comment:

TODO(miu): Merge "AssociateWithProducer" message into "CreateStream" message so
AudioRendererHost can assume a simpler "render_view_id is set once" scheme. 
http://crbug.com/166779

[Bernhard Bauer, 2013/02/05 18:45:18]

Done.

 }
 
 void AudioRendererHost::OnPlayStream(int stream_id) {
@@ -302,7 +313,8 @@ void AudioRendererHost::OnPlayStream(int stream_id) {
 
   entry->controller->Play();
   if (media_observer_)
-    media_observer_->OnSetAudioStreamPlaying(this, stream_id, true);
+    media_observer_->OnSetAudioStreamPlaying(
+        this, stream_id, render_process_id_, entry->render_view_id, true);
 }
 
 void AudioRendererHost::OnPauseStream(int stream_id) {
@@ -315,8 +327,10 @@ void AudioRendererHost::OnPauseStream(int stream_id) {
   }
 
   entry->controller->Pause();
-  if (media_observer_)
-    media_observer_->OnSetAudioStreamPlaying(this, stream_id, false);
+  if (media_observer_) {
+    media_observer_->OnSetAudioStreamPlaying(
+        this, stream_id, render_process_id_, entry->render_view_id, false);
+  }
 }
 
 void AudioRendererHost::OnFlushStream(int stream_id) {