Add mojo interface for audio rendering.

content/browser/renderer_host/media/audio_output_impl.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_impl.h"
+
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <utility>
+
+#include "base/memory/shared_memory.h"
+#include "content/browser/media/capture/audio_mirroring_manager.h"
+#include "mojo/public/cpp/system/platform_handle.h"
+
+namespace content {
+
+// static
+AudioOutputImpl::UniquePtr AudioOutputImpl::Create(
+    base::SingleThreadTaskRunner* task_runner,
+    Host* host,
+    int32_t id,
+    int render_frame_id,
+    int render_process_id,
+    const std::string& output_device_id) {
+  return UniquePtr(new AudioOutputImpl(task_runner, host, id, render_frame_id,
+                                       render_process_id, output_device_id),
+                   Deleter());
+}
+
+AudioOutputImpl::~AudioOutputImpl() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+}
+
+void AudioOutputImpl::Bind(media::mojom::AudioOutputRequest request) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  binding_.Bind(std::move(request));
+  binding_.set_connection_error_handler(
+      base::Bind(&AudioOutputImpl::OnError, base::Unretained(this)));
+}
+
+void AudioOutputImpl::Close() {
+  // Since AudioOutputController is closed asynchronously, we need to take
+  // extra care when AudioOutputImpl is deleted. We use a custom deleter for
+  // our unique_ptrs to make this extra trouble transparent to the owner.
+  // The entire termination sequence is like this:
+  // 1. Close is called and we unbind ourselves, if bound.
+  // 2. We ask the AudioOutputService to remove us.
+  // 3. AudioOutputService removes its reference, causing Deleter::operator()
+  // to run.
+  // 4. a. Deleter closes controller_, which then deletes us by callback.
+  //    b. There is no controller, so Deleter just deletes us.
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (is_closing)
+    return;
+  is_closing = true;
+  binding_.Close();
+  if (IsStarted())
+    host_->NotifyStreamClosed(id_);
+  host_->Remove(id_);
+}
+
+void AudioOutputImpl::Start(const media::AudioParameters& params,
+                            const StartCallback& callback) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(!is_closing);
+  if (IsStarted()) {
+    Close();
+    return;
+  }
+  Init(params);
+  if (!IsStarted()) {
+    Close();
+    return;
+  }
+
+  host_->NotifyStreamCreated(id_, controller_.get(), render_frame_id_);
+  // We add the controller to AudioMirroringManager in this class since we
+  // have to remove it in this class.
+  content::AudioMirroringManager::GetInstance()->AddDiverter(
+      render_process_id_, render_frame_id_, controller_.get());
+
+  controller_->Play();
+  start_callback_ = std::move(callback);
+}
+
+void AudioOutputImpl::Play() {
+  DCHECK(!is_closing);
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (!IsStarted())
+    Close();

[o1ka, 2016/09/28 10:24:06]

Here and in other places: what is the purpose of Close() here? Is it error
processing? Would DCHECKs be enough? Anyways, some logging and comments needed
to explain what has happened

[Max Morin, 2016/09/28 12:47:33]

Ok, in this case the client might call Play() before Start(), which is an error
of the client, not something we should DCHECK on.

+  else
+    controller_->Play();
+}
+
+void AudioOutputImpl::Pause() {
+  DCHECK(!is_closing);
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (!IsStarted())
+    Close();
+  else
+    controller_->Pause();
+}
+
+void AudioOutputImpl::SetVolume(double volume) {
+  DCHECK(!is_closing);
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (!IsStarted() || volume < 0.0 || volume > 1.0)

[o1ka, 2016/09/28 10:24:07]

Where these volume limits come from? And what if they change there?

[Max Morin, 2016/09/28 12:47:33]

Good question. Needs better comments.

+    Close();
+  else
+    controller_->SetVolume(volume);
+}
+
+void AudioOutputImpl::OnCreated() {
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&AudioOutputImpl::DoCompleteCreation, base::Unretained(this)));

[o1ka, 2016/09/28 10:24:07]

"this" won't survive

+}
+
+void AudioOutputImpl::OnPlaying() {

[o1ka, 2016/09/28 10:24:07]

Thread check?  and what if it is called after Close has been executed?

+  host_->NotifyStreamStateChanged(id_, true);
+}
+void AudioOutputImpl::OnPaused() {
+  host_->NotifyStreamStateChanged(id_, false);

[o1ka, 2016/09/28 10:24:06]

Same as above

+}
+void AudioOutputImpl::OnError() {
+  task_runner_->PostTask(
+      FROM_HERE, base::Bind(&AudioOutputImpl::Close, base::Unretained(this)));

[o1ka, 2016/09/28 10:24:06]

What is the guarantee that "this" will survive until Close() execution? (looks
like there is none)

[Max Morin, 2016/09/28 12:47:33]

Ok, so we should maybe have weak pointers to *this. I'll think more.

+}
+
+AudioOutputImpl::AudioOutputImpl(base::SingleThreadTaskRunner* task_runner,
+                                 Host* host,
+                                 int32_t id,
+                                 int render_frame_id,
+                                 int render_process_id,
+                                 const std::string& output_device_id)
+    : task_runner_(task_runner),
+      host_(host),
+      id_(id),
+      render_frame_id_(render_frame_id),
+      render_process_id_(render_process_id),
+      output_device_id_(output_device_id),
+      binding_(this) {
+  DCHECK(task_runner_->BelongsToCurrentThread());

[o1ka, 2016/09/28 10:24:07]

Do you really need it to be constructed on this thread? If so, you don't need
task_runner as a parameter, you can just use the current one.

+}
+
+void AudioOutputImpl::DoCompleteCreation() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (is_closing)

[o1ka, 2016/09/28 10:24:06]

is it actually "closing" or "closed"?

[Max Morin, 2016/09/28 12:47:33]

I'll rework this bit.

+    return;
+  DCHECK(reader_);
+  DCHECK(binding_.is_bound());
+
+  // Now construction is done and we are ready to send the shared memory and the
+  // sync socket to the renderer.
+  base::SharedMemory* shared_memory = reader_->shared_memory();
+  base::CancelableSyncSocket* foreign_socket = reader_->foreign_socket();
+  DCHECK(shared_memory);
+  DCHECK(foreign_socket);
+
+  // Wrap the shared memory for sending:
+  base::SharedMemoryHandle foreign_memory_handle =
+      base::SharedMemory::DuplicateHandle(shared_memory->handle());
+  // TODO: When does this fail?
+  DCHECK(base::SharedMemory::IsHandleValid(foreign_memory_handle))
+      << "Invalid memory handle.";
+  mojo::ScopedSharedBufferHandle shared_buffer_handle =
+      mojo::WrapSharedMemoryHandle(foreign_memory_handle,
+                                   shared_memory->requested_size(), false);
+
+  // TODO: When does this fail?
+  DCHECK(shared_buffer_handle.is_valid());
+
+  // TODO: take ownership of sync socket handle, crbug.com/647659
+  start_callback_.Run(std::move(shared_buffer_handle),
+                      mojo::WrapPlatformFile(foreign_socket->handle()));
+}
+
+void AudioOutputImpl::Init(const media::AudioParameters& params) {
+  DCHECK(!is_closing);
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  reader_ = AudioSyncReader::Create(params);
+  if (!reader_)
+    return;

[o1ka, 2016/09/28 10:24:06]

Is it a normal situation? If not - DCHECK? (we can't fail silently)

[Max Morin, 2016/09/28 12:47:33]

Should probably be a DCHECK, it happens if we can't allocate shared memory (out
of memory?) or if we can't make a socket pair (probably too many file
descriptors?).

+  controller_ = media::AudioOutputController::Create(
+      media::AudioManager::Get(), this, params, output_device_id_,
+      reader_.get());
+  DCHECK(controller_);
+}
+
+bool AudioOutputImpl::IsStarted() const {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  return controller_ != nullptr;
+}
+
+void AudioOutputImpl::Deleter::operator()(AudioOutputImpl* output) {
+  DCHECK(output->task_runner_->BelongsToCurrentThread());
+  DCHECK(output->is_closing);
+  if (output->controller_)
+    output->controller_->Close(base::Bind(&AudioOutputImpl::DeleteAndUnregister,
+                                          base::Unretained(output)));
+  else
+    delete output;
+}
+
+// static
+void AudioOutputImpl::DeleteAndUnregister(AudioOutputImpl* output) {
+  // This must be done after controller finished closing, see
+  // http://crbug.com/474432.
+  AudioMirroringManager::GetInstance()->RemoveDiverter(
+      output->controller_.get());
+  output->task_runner_->DeleteSoon(FROM_HERE, output);

[o1ka, 2016/09/28 10:24:06]

This deletion is a lot of fun, but can we probably simplify it?

+}
+
+}  // namespace content