chromecast: add protobuf file

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/stream_out/chromecast/cast_channel.proto

+// Copyright 2013 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.
+
+syntax = "proto2";
+
+option optimize_for = LITE_RUNTIME;
+
+package castchannel;
+
+message CastMessage {
+  // Always pass a version of the protocol for future compatibility
+  // requirements.
+  enum ProtocolVersion {
+    CASTV2_1_0 = 0;
+  }
+  required ProtocolVersion protocol_version = 1;
+
+  // source and destination ids identify the origin and destination of the
+  // message.  They are used to route messages between endpoints that share a
+  // device-to-device channel.
+  //
+  // For messages between applications:
+  //   - The sender application id is a unique identifier generated on behalf of
+  //     the sender application.
+  //   - The receiver id is always the the session id for the application.
+  //
+  // For messages to or from the sender or receiver platform, the special ids
+  // 'sender-0' and 'receiver-0' can be used.
+  //
+  // For messages intended for all endpoints using a given channel, the
+  // wildcard destination_id '*' can be used.
+  required string source_id = 2;
+  required string destination_id = 3;
+
+  // This is the core multiplexing key.  All messages are sent on a namespace
+  // and endpoints sharing a channel listen on one or more namespaces.  The
+  // namespace defines the protocol and semantics of the message.
+  required string namespace = 4;
+
+  // Encoding and payload info follows.
+
+  // What type of data do we have in this message.
+  enum PayloadType {
+    STRING = 0;
+    BINARY = 1;
+  }
+  required PayloadType payload_type = 5;
+
+  // Depending on payload_type, exactly one of the following optional fields
+  // will always be set.
+  optional string payload_utf8 = 6;
+  optional bytes payload_binary = 7;
+}
+
+// Messages for authentication protocol between a sender and a receiver.
+message AuthChallenge {
+}
+
+message AuthResponse {
+  required bytes signature = 1;
+  required bytes client_auth_certificate = 2;
+}
+
+message AuthError {
+  enum ErrorType {
+    INTERNAL_ERROR = 0;
+    NO_TLS = 1;  // The underlying connection is not TLS
+  }
+  required ErrorType error_type = 1;
+}
+
+message DeviceAuthMessage {
+  // Request fields
+  optional AuthChallenge challenge = 1;
+  // Response fields
+  optional AuthResponse response = 2;
+  optional AuthError error = 3;
+}
\ No newline at end of file