Use AudioStreamMonitor to control power save blocking.

content/browser/web_contents/web_contents_impl.cc

Index: content/browser/web_contents/web_contents_impl.cc
diff --git a/content/browser/web_contents/web_contents_impl.cc b/content/browser/web_contents/web_contents_impl.cc
index 350f586d8dcd797d337b9559cf1ffad54f483f21..d6c3c3c216cb04a0c28df0aeb55ed6f2cc0e77c2 100644
--- a/content/browser/web_contents/web_contents_impl.cc
+++ b/content/browser/web_contents/web_contents_impl.cc
@@ -3004,15 +3004,15 @@ void WebContentsImpl::OnUpdateFaviconURL(
 void WebContentsImpl::OnMediaPlayingNotification(int64 player_cookie,
                                                  bool has_video,
                                                  bool has_audio) {
-#if !defined(OS_CHROMEOS)
+  // Power save blocking is controlled by the tab audio indicator on desktop
+  // platforms.
+#if !defined(OS_CHROMEOS) && defined(OS_ANDROID)
   scoped_ptr<PowerSaveBlocker> blocker;
   if (has_video) {
     blocker = PowerSaveBlocker::Create(
         PowerSaveBlocker::kPowerSaveBlockPreventDisplaySleep, "Playing video");

[scherkus (not reviewing), 2014/08/21 21:42:55]

FYI this is prevent display sleep

-#if defined(OS_ANDROID)
     static_cast<PowerSaveBlockerImpl*>(blocker.get())
         ->InitDisplaySleepBlocker(GetView()->GetNativeView());
-#endif
   } else if (has_audio) {
     blocker = PowerSaveBlocker::Create(
         PowerSaveBlocker::kPowerSaveBlockPreventAppSuspension, "Playing audio");

[scherkus (not reviewing), 2014/08/21 21:42:55]

FYI this is the audio-only branch which only prevents app suspension

I'm not sure what the actual impact is between the two

[miu, 2014/08/25 19:34:52]

note: It should be perfectly safe to have multiple and different
PowerSaveBlockers around at the same time.