Use AudioStreamMonitor to control power save blocking.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 2986 matching lines @@
 
 void WebContentsImpl::OnUpdateFaviconURL(
     const std::vector<FaviconURL>& candidates) {
   FOR_EACH_OBSERVER(WebContentsObserver, observers_,
                     DidUpdateFaviconURL(candidates));
 }
 
 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.

   }
 
   if (blocker) {
     uintptr_t key = reinterpret_cast<uintptr_t>(render_frame_message_source_);
     if (!power_save_blockers_.contains(key)) {
       power_save_blockers_.add(key,
                                make_scoped_ptr(new PowerSaveBlockerMapEntry));
     }
     PowerSaveBlockerMapEntry* map_entry =
         power_save_blockers_.get(key);
@@ skipping 1213 matching lines @@
   node->render_manager()->ResumeResponseDeferredAtStart();
 }
 
 void WebContentsImpl::SetForceDisableOverscrollContent(bool force_disable) {
   force_disable_overscroll_content_ = force_disable;
   if (view_)
     view_->SetOverscrollControllerEnabled(CanOverscrollContent());
 }
 
 }  // namespace content