Media Remoting: Add mojo interfaces between browser and extension.

media/mojo/interfaces/mirror_service_remoting.mojom

+// 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.
+
+module media.mojom;
+
+import "media/mojo/interfaces/remoting_common.mojom";
+
+// Interface used by the source to start/stop remoting and send data to the
+// sink.
+interface MirrorServiceRemoter {
+  // Starts a remoting session. Always assumes the remoting session will be
+  // stared successfully. Once any failure happens,

[miu, 2017/06/27 00:23:49]

nit: s/Once/If/ Let's be optimistic, eh? :-)

[xjz, 2017/06/28 02:09:39]

Done.

+  // MirrorServiceRemotingSource::OnError() will be called.
+  Start();
+
+  // Starts remoting the media data streams. This is called after Start() to
+  // indicate audio/video bitstream data is ready to be consumed.
+  StartDataStreams(bool has_audio, bool has_video);

[miu, 2017/06/27 00:23:49]

Suggestion: This should return values so that the stream IDs aren't decoupled
from the StartDataStreamsCall(). Meaning:

  StartDataStreams(bool audio, bool video) --> (int32 audio_stream_id, int32
video_stream_id);

See comments in cast_remoting_connector.cc for more details.

[xjz, 2017/06/28 02:09:39]

Done.

+
+  // Stops remoting media. Messages in both directions will be dropped after this

[miu, 2017/06/27 00:23:49]

80 chars. (run `git cl format`?)

[xjz, 2017/06/28 02:09:39]

Done.

+  // point as well as any pending or in-transit media bitstream data.
+  Stop(media.mojom.RemotingStopReason reason);
+
+  // Sends|message| to the sink. |message| is a serialized protobuf from
+  // src/media/remoting/proto.
+  SendMessageToSink(array<uint8> message);
+};
+
+// Interface used for sending notifications back to the source's control logic,
+// and to pass messages from the sink back to the source.
+interface MirrorServiceRemotingSource {
+  // Notifies the source that the sink is now available to start remoting. It is
+  // up to the source's control logic to decide whether/when to start remoting.
+  OnSinkAvailable(media.mojom.RemotingSinkCapabilities capabilities);
+
+  // Called after the remoting data streams are created. Setting the
+  // |audio/video_stream_id| to -1 indicates there is no audio/video stream.
+  OnDataStreamsStarted(int32 audio_stream_id, int32 video_stream_id);

[miu, 2017/06/27 00:23:49]

Per the suggestion above, you can remove this.

[xjz, 2017/06/28 02:09:39]

Done.

+
+  // Passes a |message| from the sink back to the source. The |message| consists
+  // of a serialized protobuf from src/media/remoting/proto. This will only be
+  // called after OnStarted() and before OnStopped().
+  OnMessageFromSink(array<uint8> message);
+
+  // Notifies the source that remoting has terminated. This may or may not be in
+  // response to a Remoter.Stop() call, as other events (possibly external) may
+  // have caused remoting to end.
+  OnStopped(media.mojom.RemotingStopReason reason);
+
+  // Notifies the source that fatal error occurs. Remoting session will be

[miu, 2017/06/27 00:23:49]

nit: s/that fatal error occurs/that a fatal error has occurred/

[xjz, 2017/06/28 02:09:39]

Done.

+  // stopped immediately once this is called.
+  OnError();
+};