Add mojo interface for audio rendering.

content/common/media/audio_output.mojom

+// 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.
+
+module content.mojom;
+
+import "media/mojo/interfaces/audio_parameters.mojom";
+import "media/mojo/interfaces/media_types.mojom";
+import "url/mojo/origin.mojom";
+
+// On error, the message pipe is closed.
+// To close the stream, just close the message pipe.
+interface AudioOutput {
+  Start(media.mojom.AudioParameters params) =>
+       (handle<shared_buffer> shared_buffer,
+        handle socket_descriptor);
+  Play();
+  Pause();
+  // Volume is in the range [0, 1].
+  SetVolume(double volume);
+};
+
+interface RendererAudioOutputService {
+  // Used to request a device.
+  // An AudioOutputRequest may be supplied, in which case it will
+  // be bound to an AudioOutput implementation or closed (in case of an error).
+  // TODO better name.
+  RequestDeviceAuthorization(
+      AudioOutput&? audio_output_request,
+      int64 session_id,
+      string device_id,
+      url.mojom.Origin origin) =>
+      (media.mojom.OutputDeviceStatus state,
+       media.mojom.AudioParameters output_params,
+       string matched_device_id);
+};