Add mojo interface+impl for audio stream control.

media/mojo/interfaces/audio_output.mojom

Index: media/mojo/interfaces/audio_output.mojom
diff --git a/media/mojo/interfaces/audio_output.mojom b/media/mojo/interfaces/audio_output.mojom
index 895a93e4967727e4d2846679b50433a2de46ff94..150ace22d9e2981fd0c8ae3b5288f133c5064870 100644
--- a/media/mojo/interfaces/audio_output.mojom
+++ b/media/mojo/interfaces/audio_output.mojom
@@ -5,29 +5,24 @@
 module media.mojom;
 
 import "media/mojo/interfaces/audio_parameters.mojom";
+import "media/mojo/interfaces/media_types.mojom";
 
-// This interface handles audio output stream operations.
-// It allows to close a stream.
-// TODO(rchtara): Add methods that allow the interaction with audio output
-// streams: Play, Pause and SetVolume to this interface.
-// See crbug.com/606707 for more details.
-interface AudioOutputStream {
-  Close();
-};
-
-// This interface manages audio output streams.
-// It allows to create an AudioOutputStream.
-// TODO(rchtara): Add a method to request device authorization to this
-// interface.
-// See crbug.com/606707 for more details.
+// An interface for creating and controlling an output stream.
 interface AudioOutput {
-  // TODO(rchtara): Remove |stream_id| from AudioOutput::CreateStream when all
-  // the stream operations are mojofied.
-  CreateStream(
-      int32 stream_id,
-      AudioParameters params) =>
-      (int32 stream_id,
-       AudioOutputStream? stream,
-       handle<shared_buffer>? shared_buffer,
-       handle? socket_descriptor);
-};
+  // On error, the message pipe is closed.
+  // To close the stream, just close the message pipe.
+
+  // Initializes the stream using |params|. |shared_buffer| and |socket_descriptor|
+  // is used to write data to the stream as defined in AudioDeviceThread.

[o1ka, 2017/02/22 13:26:30]

nit: are used

[Max Morin, 2017/03/02 23:11:32]

Done.

+  // Initialize must be called once before other methods may be called.
+  Initialize(media.mojom.AudioParameters params) =>
+       (handle<shared_buffer> shared_buffer,
+        handle socket_descriptor);
+  // Starts rendering audio.
+  Play();
+  // Stops rendering audio and sends a signal to the |socket_descriptor|
+  // indicating this.
+  Pause();
+  // Sets volume. Volume is in the range [0, 1].

[o1ka, 2017/02/22 13:26:30]

Describe what happens if volume if out of range?

[Max Morin, 2017/03/02 23:11:32]

It's not allowed.

+  SetVolume(double volume);
+};