Use AudioStreamMonitor to control power save blocking.

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 91cea8365224cc79a0625c6c0793c778f053d59b..bd4e0f11e10c6ecdcf4f305d7ac32d71e515d014 100644
--- a/content/browser/renderer_host/media/audio_renderer_host.cc
+++ b/content/browser/renderer_host/media/audio_renderer_host.cc
@@ -23,6 +23,13 @@
 #include "media/base/audio_bus.h"
 #include "media/base/limits.h"
 
+// Only do audio stream monitoring for platforms that use it for the tab media
+// indicator UI or the OOM killer.
+#if !defined(OS_ANDROID) && !defined(OS_IOS)
+#define AUDIO_STREAM_MONITORING

[DaleCurtis, 2014/08/29 23:56:47]

It's unfortunate to define this everywhere. I'm open to suggestions such as
stubbing out the ASM methods for Android/IOS so multiple places don't have this
define gunk.

+#include "content/browser/media/audio_stream_monitor.h"
+#endif
+
 using media::AudioBus;
 using media::AudioManager;
 
@@ -272,28 +279,29 @@ void AudioRendererHost::DoNotifyStreamStateChanged(int stream_id,
       is_playing ? media::AudioOutputIPCDelegate::kPlaying
                  : media::AudioOutputIPCDelegate::kPaused));
 
-  MediaObserver* const media_observer =
-      GetContentClient()->browser()->GetMediaObserver();
-  if (media_observer) {
-    if (is_playing) {
-      media_observer->OnAudioStreamPlaying(
-          render_process_id_,
-          entry->render_frame_id(),
-          entry->stream_id(),
-          base::Bind(&media::AudioOutputController::ReadCurrentPowerAndClip,
-                     entry->controller()));
-      if (!entry->playing()) {
-        entry->set_playing(true);
-        base::AtomicRefCountInc(&num_playing_streams_);
-      }
-    } else {
-      media_observer->OnAudioStreamStopped(render_process_id_,
-                                           entry->render_frame_id(),
-                                           entry->stream_id());
-      if (entry->playing()) {
-        entry->set_playing(false);
-        base::AtomicRefCountDec(&num_playing_streams_);
-      }
+  if (is_playing) {
+#if defined(AUDIO_STREAM_MONITORING)
+    AudioStreamMonitor::StartMonitoringStream(
+        render_process_id_,
+        entry->render_frame_id(),
+        entry->stream_id(),
+        base::Bind(&media::AudioOutputController::ReadCurrentPowerAndClip,
+                   entry->controller()));
+#endif
+    // TODO(dalecurtis): See about using AudioStreamMonitor instead.
+    if (!entry->playing()) {
+      entry->set_playing(true);
+      base::AtomicRefCountInc(&num_playing_streams_);
+    }
+  } else {
+#if defined(AUDIO_STREAM_MONITORING)
+    AudioStreamMonitor::StopMonitoringStream(
+        render_process_id_, entry->render_frame_id(), entry->stream_id());
+#endif
+    // TODO(dalecurtis): See about using AudioStreamMonitor instead.
+    if (entry->playing()) {
+      entry->set_playing(false);
+      base::AtomicRefCountDec(&num_playing_streams_);
     }
   }
 }
@@ -463,17 +471,12 @@ void AudioRendererHost::OnCloseStream(int stream_id) {
 
 void AudioRendererHost::DeleteEntry(scoped_ptr<AudioEntry> entry) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
-
-  // At this point, make the final "say" in audio playback state.
-  MediaObserver* const media_observer =
-      GetContentClient()->browser()->GetMediaObserver();
-  if (media_observer) {
-    media_observer->OnAudioStreamStopped(render_process_id_,
-                                         entry->render_frame_id(),
-                                         entry->stream_id());
-    if (entry->playing())
-      base::AtomicRefCountDec(&num_playing_streams_);
-  }
+#if defined(AUDIO_STREAM_MONITORING)
+  AudioStreamMonitor::StopMonitoringStream(
+      render_process_id_, entry->render_frame_id(), entry->stream_id());
+#endif
+  if (entry->playing())
+    base::AtomicRefCountDec(&num_playing_streams_);
 }
 
 void AudioRendererHost::ReportErrorAndClose(int stream_id) {