Cast audio only policy enforcement support.

extensions/common/api/cast_channel.idl

 // Copyright 2014 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.
 
 // API for communicating with a Google Cast device over an authenticated
 // channel.
 namespace cast.channel {
 
   // The state of the channel.
   enum ReadyState {
@@ skipping 55 matching lines @@
     // The port number to connect to, 0-65535.
     long port;
 
     // The amount of time to wait in milliseconds before stopping the
     // connection process. Timeouts are disabled if the value is zero.
     // The default timeout is 8000ms.
     long? timeout;
 
     // The authentication method required for the channel.
     ChannelAuthType auth;
+
+    // If set, a bit mask describing capability of the cast device.

[mark a. foltz, 2015/01/12 22:01:57]

A more self documenting API would accept an array of capability enums and
internally convert it to a bitmask for the protocol.  The downside is that we
would need to convert the IDL generated enum (which will be numbered 0 ... N-1)
to the bit shifted values internally.  I can see it either way.

If you stay with the bitmask, then please add a pointer to the canonical
definition of the values.

[vadimgo, 2015/01/13 00:08:27]

Now refer to the mask type in the comment.

+    long? capabilities;
   };
 
   // Describes the state of a channel to a Cast receiver.
   dictionary ChannelInfo {
     // Id for the channel.
     long channelId;
 
     // DEPRECATED: The URL to the receiver.  This field will be removed in a
     // future release.
     DOMString url;
@@ skipping 124 matching lines @@
   interface Events {
     // Fired when a message is received on an open channel.
     static void onMessage(ChannelInfo channel,
                           MessageInfo message);
 
     // Fired when an error occurs as a result of a channel operation or a
     // network event. |error| contains details of the error.
     static void onError(ChannelInfo channel, ErrorInfo error);
   };
 };