Add mojo interface+impl for audio stream control.

media/mojo/services/mojo_audio_output_stream_provider.cc

+// Copyright 2017 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 "media/mojo/services/mojo_audio_output_stream_provider.h"
+
+#include <utility>
+
+namespace media {
+
+MojoAudioOutputStreamProvider::MojoAudioOutputStreamProvider(
+    mojom::AudioOutputStreamProviderRequest request,
+    CreateDelegateCallback create_delegate_callback,
+    DeleterCallback deleter_callback)
+    : binding_(this, std::move(request)),
+      create_delegate_callback_(std::move(create_delegate_callback)),
+      deleter_callback_(base::Bind(std::move(deleter_callback), this)) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  binding_.set_connection_error_handler(deleter_callback_);
+  DCHECK(create_delegate_callback_);
+  DCHECK(deleter_callback_);
+}
+
+MojoAudioOutputStreamProvider::~MojoAudioOutputStreamProvider() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void MojoAudioOutputStreamProvider::Acquire(
+    mojom::AudioOutputStreamRequest stream_request,
+    const AudioParameters& params,
+    const AcquireCallback& callback) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (audio_output_) {
+    LOG(ERROR) << "Output acquired twice.";
+    binding_.Unbind();
+    deleter_callback_.Run();

[o1ka, 2017/03/07 23:31:07]

Add a comment that it's deleting |this|? (so that nobody in the future would try
to add anything after that line)

[Max Morin, 2017/03/08 07:38:29]

Done.

+    return;
+  }
+
+  audio_output_.emplace(
+      std::move(stream_request),
+      base::BindOnce(std::move(create_delegate_callback_), params),
+      std::move(callback), deleter_callback_);
+}
+
+}  // namespace media