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

chrome/browser/media/media_capture_devices_dispatcher.cc

Index: chrome/browser/media/media_capture_devices_dispatcher.cc
diff --git a/chrome/browser/media/media_capture_devices_dispatcher.cc b/chrome/browser/media/media_capture_devices_dispatcher.cc
index f1d616534a113312ccd9546d6c3cf81021fd4688..7b2e6939d6761e26b5c3f8bc3ad4959a60363c0e 100644
--- a/chrome/browser/media/media_capture_devices_dispatcher.cc
+++ b/chrome/browser/media/media_capture_devices_dispatcher.cc
@@ -5,6 +5,7 @@
 #include "chrome/browser/media/media_capture_devices_dispatcher.h"
 
 #include "base/prefs/pref_service.h"
+#include "chrome/browser/media/audio_stream_indicator.h"
 #include "chrome/browser/media/media_stream_capture_indicator.h"
 #include "chrome/browser/prefs/pref_registry_syncable.h"
 #include "chrome/browser/prefs/scoped_user_pref_update.h"
@@ -44,7 +45,8 @@ MediaCaptureDevicesDispatcher* MediaCaptureDevicesDispatcher::GetInstance() {
 
 MediaCaptureDevicesDispatcher::MediaCaptureDevicesDispatcher()
     : devices_enumerated_(false),
-      media_stream_capture_indicator_(new MediaStreamCaptureIndicator()) {}
+      media_stream_capture_indicator_(new MediaStreamCaptureIndicator()),
+      audio_stream_indicator_(new AudioStreamIndicator()) {}
 
 MediaCaptureDevicesDispatcher::~MediaCaptureDevicesDispatcher() {}
 
@@ -149,6 +151,11 @@ scoped_refptr<MediaStreamCaptureIndicator>
   return media_stream_capture_indicator_;
 }
 
+scoped_refptr<AudioStreamIndicator>
+MediaCaptureDevicesDispatcher::GetAudioStreamIndicator() {
+  return audio_stream_indicator_;
+}
+
 void MediaCaptureDevicesDispatcher::OnCaptureDevicesOpened(
     int render_process_id,
     int render_view_id,
@@ -202,6 +209,14 @@ void MediaCaptureDevicesDispatcher::OnMediaRequestStateChanged(
 
 }
 
+void MediaCaptureDevicesDispatcher::OnAudioStreamPlayingChanged(
+    int render_process_id, int render_view_id, int stream_id, bool playing) {
+  audio_stream_indicator_->UpdateWebContentsStatus(render_process_id,
+                                                   render_view_id,
+                                                   stream_id,
+                                                   playing);
+}
+
 void MediaCaptureDevicesDispatcher::UpdateAudioDevicesOnUIThread(
     const content::MediaStreamDevices& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));