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 23136c98d81809e905ba25a342765cd679c35e08..b205d176b8128e3052c176b788e9c244b71a3926 100644
--- a/chrome/browser/media/media_capture_devices_dispatcher.cc
+++ b/chrome/browser/media/media_capture_devices_dispatcher.cc
@@ -4,6 +4,7 @@
 
 #include "chrome/browser/media/media_capture_devices_dispatcher.h"
 
+#include "chrome/browser/media/audio_stream_indicator.h"
 #include "chrome/browser/media/media_stream_capture_indicator.h"
 #include "chrome/browser/prefs/scoped_user_pref_update.h"
 #include "chrome/browser/profiles/profile.h"
@@ -42,7 +43,8 @@ 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() {}
 
@@ -145,6 +147,11 @@ 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,
@@ -198,6 +205,13 @@ void MediaCaptureDevicesDispatcher::OnMediaRequestStateChanged(
 
 }
 
+void MediaCaptureDevicesDispatcher::OnAudioStreamPlayingChanged(
+    int render_process_id, int render_view_id, bool playing) {
+  audio_stream_indicator_->UpdateWebContentsStatus(render_process_id,
+                                                   render_view_id,
+                                                   playing);
+}
+
 void MediaCaptureDevicesDispatcher::UpdateAudioDevicesOnUIThread(
     const content::MediaStreamDevices& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));