Factor out AudioOutputDelegate from AudioRendererHost.

content/browser/renderer_host/media/audio_output_delegate.cc

+// Copyright 2016 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_output_delegate.h"
+
+#include "base/bind.h"
+#include "content/browser/media/audio_stream_monitor.h"
+#include "content/browser/media/media_internals.h"
+#include "content/browser/renderer_host/media/audio_sync_reader.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace {
+void RemoveDiverter(content::AudioMirroringManager* mirroring_manager,
+                    scoped_refptr<media::AudioOutputController> controller) {
+  // De-register the controller from the AudioMirroringManager now that the
+  // controller has closed the AudioOutputStream and shut itself down. This
+  // ensures that calling RemoveDiverter() here won't trigger the controller to
+  // re-start the default AudioOutputStream and cause a brief audio blip to come
+  // out the user's speakers. http://crbug.com/474432
+  mirroring_manager->RemoveDiverter(controller.get());
+}
+}  //  namespace
+
+namespace content {
+
+AudioOutputDelegate::AudioOutputDelegate(
+    EventHandler* handler,
+    media::AudioLog* audio_log,
+    AudioMirroringManager* mirroring_manager,
+    MediaObserver* media_observer,
+    int stream_id,
+    int render_frame_id,
+    int render_process_id,
+    media::AudioParameters params,
+    const std::string& output_device_id)
+    : handler_(handler),
+      audio_log_(audio_log),

[o1ka, 2016/10/25 12:32:34]

It's probably fine to have an individual audio_log per AudioOutputDelegate,
because it's just an accessor to media log, and this way you don't need to care
about audio_log lifetime.

[Max Morin, 2016/10/26 09:20:17]

Done.

+      mirroring_manager_(mirroring_manager),
+      controller_(media::AudioOutputController::Create(
+          media::AudioManager::Get(),
+          this,
+          params,
+          output_device_id,
+          AudioSyncReader::Create(params))),
+      stream_id_(stream_id),
+      render_frame_id_(render_frame_id),
+      render_process_id_(render_process_id),
+      weak_factory_(this) {
+  DCHECK(controller_);
+  if (media_observer)
+    media_observer->OnCreatingAudioStream(render_process_id_, render_frame_id_);
+  if (mirroring_manager_)
+    mirroring_manager_->AddDiverter(render_process_id_, render_frame_id_,
+                                    controller_.get());
+  audio_log_->OnCreated(stream_id, params, output_device_id);
+  MediaInternals::GetInstance()->SetWebContentsTitleForAudioLogEntry(
+      stream_id_, render_process_id_, render_frame_id_, audio_log_);
+}
+
+AudioOutputDelegate::~AudioOutputDelegate() {}

[o1ka, 2016/10/25 12:32:34]

AudioOutputController is refcounted, so it may now be pointing to invalid
memory. Let's implement the fix we discussed offline.

[Max Morin, 2016/10/26 09:20:17]

Done.

+
+void AudioOutputDelegate::OnPlayStream() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  controller_->Play();
+  audio_log_->OnStarted(stream_id_);
+}
+
+void AudioOutputDelegate::OnPauseStream() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  controller_->Pause();
+  audio_log_->OnStopped(stream_id_);
+}
+
+void AudioOutputDelegate::OnSetVolume(double volume) {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  controller_->SetVolume(volume);
+  audio_log_->OnSetVolume(stream_id_, volume);
+}
+
+void AudioOutputDelegate::OnCloseStream() {
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  if (playing_) {
+    handler_->OnStreamStateChanged(false);
+    playing_ = false;
+  }
+  AudioStreamMonitor::StopMonitoringStream(render_process_id_, render_frame_id_,
+                                           stream_id_);
+  if (mirroring_manager_)
+    controller_->Close(base::Bind(
+        &RemoveDiverter, base::Unretained(mirroring_manager_), controller_));

[o1ka, 2016/10/25 12:32:34]

Unretained is dangerous: no obvious guarantee that mirror_manager still exists
when RemoveDiverter() is executed.
Safer to make RemoveDiverter() to be a method of AudioOutputDelegate andpass
delegate as weak_ptr - this way you have one place less to worry about 
mirroring_manager lifetime.

[Max Morin, 2016/10/26 09:20:17]

Done.

+  else
+    controller_->Close(base::Bind([]() {}));

[o1ka, 2016/10/25 12:32:34]

base::Bind(&DoNothing) is a common way
https://cs.chromium.org/chromium/src/base/bind_helpers.h?dr=C&sq=package:chro...

[Max Morin, 2016/10/26 09:20:17]

Acknowledged.

+  audio_log_->OnClosed(stream_id_);
+}
+
+void AudioOutputDelegate::OnControllerCreated() {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(&AudioOutputDelegate::OnControllerCreated,
+                   weak_factory_.GetWeakPtr()));
+    return;
+  }
+  AudioSyncReader* reader =
+      static_cast<AudioSyncReader*>(controller_->reader());
+  handler_->OnStreamCreated(stream_id_, reader->shared_memory(),
+                            reader->foreign_socket());
+}
+
+void AudioOutputDelegate::OnControllerPlaying() {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(&AudioOutputDelegate::OnControllerPlaying,
+                   weak_factory_.GetWeakPtr()));
+    return;
+  }
+  if (!playing_) {
+    handler_->OnStreamStateChanged(true);
+    playing_ = true;
+  }
+  AudioStreamMonitor::StartMonitoringStream(
+      render_process_id_, render_frame_id_, stream_id_,
+      base::Bind(&media::AudioOutputController::ReadCurrentPowerAndClip,
+                 controller_));
+}
+
+void AudioOutputDelegate::OnControllerPaused() {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                            base::Bind(&AudioOutputDelegate::OnControllerPaused,
+                                       weak_factory_.GetWeakPtr()));
+    return;
+  }
+  if (playing_) {
+    handler_->OnStreamStateChanged(false);
+    playing_ = false;
+  }
+  AudioStreamMonitor::StopMonitoringStream(render_process_id_, render_frame_id_,
+                                           stream_id_);
+}
+
+void AudioOutputDelegate::OnControllerError() {
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(BrowserThread::IO, FROM_HERE,
+                            base::Bind(&AudioOutputDelegate::OnControllerError,
+                                       weak_factory_.GetWeakPtr()));
+    return;
+  }
+  audio_log_->OnError(stream_id_);
+  handler_->OnStreamError(stream_id_);
+}
+
+}  // namespace content