Fixed the audio backgrounding bug

content/browser/renderer_host/media/audio_renderer_host.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/renderer_host/media/audio_renderer_host.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/logging.h"
 #include "base/memory/shared_memory.h"
@@ skipping 633 matching lines @@
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (entry->playing() == is_playing)
     return;
 
   bool should_alert_resource_scheduler;
   if (is_playing) {
     should_alert_resource_scheduler =
         !RenderFrameHasActiveAudio(entry->render_frame_id());
     entry->set_playing(true);
     base::AtomicRefCountInc(&num_playing_streams_);
+
+    // If it's the first audio stream to start for this renderer.
+    if (base::AtomicRefCountIsOne(&num_playing_streams_)) {
+      RenderProcessHost* render_process_host =
+          RenderProcessHost::FromID(render_process_id_);
+
+      BrowserThread::PostTask(
+          BrowserThread::UI, FROM_HERE,
+          base::Bind(&RenderProcessHost::AudioStarted,
+                     base::Unretained(render_process_host)));
+    }
   } else {
     entry->set_playing(false);
     should_alert_resource_scheduler =
         !RenderFrameHasActiveAudio(entry->render_frame_id());
     base::AtomicRefCountDec(&num_playing_streams_);
+
+    // If it was the last audio stream playing for this renderer.
+    if (base::AtomicRefCountIsZero(&num_playing_streams_)) {

[DaleCurtis, 2015/06/29 22:21:40]

You can use the result of AtomicRefCountDec instead of doing a whole new atomic
operation.

[sebsg, 2015/06/29 22:35:00]

Done.

+      RenderProcessHost* render_process_host =
+          RenderProcessHost::FromID(render_process_id_);
+
+      BrowserThread::PostTask(
+          BrowserThread::UI, FROM_HERE,
+          base::Bind(&RenderProcessHost::AudioStopped,
+                     base::Unretained(render_process_host)));
+    }
   }
 
   if (should_alert_resource_scheduler && ResourceDispatcherHostImpl::Get()) {
     BrowserThread::PostTaskAndReplyWithResult(
         BrowserThread::UI, FROM_HERE,
         base::Bind(&RenderFrameIdToRenderViewId, render_process_id_,
                    entry->render_frame_id()),
         base::Bind(&NotifyResourceDispatcherOfAudioStateChange,
                    render_process_id_, is_playing));
   }
 }
 
 bool AudioRendererHost::HasActiveAudio() {
   return !base::AtomicRefCountIsZero(&num_playing_streams_);
 }
 
 bool AudioRendererHost::RenderFrameHasActiveAudio(int render_frame_id) const {
   for (AudioEntryMap::const_iterator it = audio_entries_.begin();
        it != audio_entries_.end();
        ++it) {
     AudioEntry* entry = it->second;
     if (entry->render_frame_id() == render_frame_id && entry->playing())
       return true;
   }
   return false;
 }
 
 }  // namespace content