Add mojo interface+impl creation of audio streams.

content/common/media/audio_output_stream_factory.mojom

+// Copyright 2016 The Chromium Authors. All rights reserved.

[o1ka, 2017/03/21 16:20:17]

2017

[Max Morin, 2017/03/22 13:18:29]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module content.mojom;
+
+import "media/mojo/interfaces/audio_output_stream.mojom";
+import "media/mojo/interfaces/audio_parameters.mojom";
+import "media/mojo/interfaces/media_types.mojom";
+import "url/mojo/origin.mojom";
+
+interface RendererAudioOutputStreamFactory {

[o1ka, 2017/03/21 16:20:17]

Should the file be named "renderer_audio_output_stream_factory.mojom" maybe?
We'll have other stream factories in the future (the one in AudioProcess, for
example)

[Max Morin, 2017/03/22 13:18:29]

Done.

+  // Used to request a device. An AudioOutputStreamProviderRequest may be
+  // supplied, in which case it will be bound to an AudioOutputStreamProvider
+  // implementation or closed (in case of an error).
+  RequestDeviceAuthorization(
+      media.mojom.AudioOutputStreamProvider&? stream_provider_request,

[o1ka, 2017/03/21 16:20:17]

Could you clarify in the comment the usecase when 
AudioOutputStreamProviderRequest is not provided?

[Max Morin, 2017/03/22 13:18:29]

Changed so that request must always be provided.

+      int64 session_id,
+      string device_id,
+      url.mojom.Origin origin) =>
+      (media.mojom.OutputDeviceStatus state,
+       media.mojom.AudioParameters output_params,
+       string matched_device_id);
+};