Communicate audio state to renderer process on Android.

content/browser/media/media_web_contents_observer.cc

Index: content/browser/media/media_web_contents_observer.cc
diff --git a/content/browser/media/media_web_contents_observer.cc b/content/browser/media/media_web_contents_observer.cc
index ef3f5dc9c9d5194480f0a5c99e351f872ac0491c..67aa481b11116c1ae458c3df5ea770d115eea3a8 100644
--- a/content/browser/media/media_web_contents_observer.cc
+++ b/content/browser/media/media_web_contents_observer.cc
@@ -43,7 +43,7 @@ void MediaWebContentsObserver::RenderFrameDeleted(
 }
 
 void MediaWebContentsObserver::MaybeUpdateAudibleState() {
-  if (!AudioStreamMonitor::monitoring_available())
+  if (!AudioStreamMonitor::power_level_monitoring_available())

[DaleCurtis, 2016/11/15 19:26:01]

I think this can be removed now as well as some of the other pieces below since
this code works on the same premise as what you've brought to the stream
monitor.

[altimin, 2016/11/16 12:52:46]

I'm a little hesitant about it — it is really a good idea to prevent Android
from entering power save mode when audio track is present? I'm afraid that we
will use more power and I'd like an explicit confirmation from someone who knows
what's happening here.

[DaleCurtis, 2016/11/16 22:16:51]

Sorry if I was unclear, there should be no behavioral change. If there is,
something is unexpected. The existing power save blocker should only be
configured when an audio stream is playing. Both implementations should now be
doing the same thing IIRC. Also I wrote all this, so I'm probably that someone
:)

[altimin, 2016/11/17 16:13:26]

Oh, I finally figured it out (previously I thought that power blocker was
enabled only on desktop).
Done.

     return;
 
   AudioStreamMonitor* audio_stream_monitor =
@@ -138,7 +138,7 @@ void MediaWebContentsObserver::OnMediaPlaying(
     // If we don't have audio stream monitoring, allocate the audio power save
     // blocker here instead of during NotifyNavigationStateChanged().
     if (!audio_power_save_blocker_ &&
-        !AudioStreamMonitor::monitoring_available()) {
+        !AudioStreamMonitor::power_level_monitoring_available()) {
       CreateAudioPowerSaveBlocker();
     }
   }
@@ -208,7 +208,7 @@ void MediaWebContentsObserver::MaybeReleasePowerSaveBlockers() {
   // monitoring, release the audio power save blocker here instead of during
   // NotifyNavigationStateChanged().
   if (active_audio_players_.empty() &&
-      !AudioStreamMonitor::monitoring_available()) {
+      !AudioStreamMonitor::power_level_monitoring_available()) {
     audio_power_save_blocker_.reset();
   }