[cast_channel] Implement CastSocketService::OpenSocket()

extensions/browser/api/cast_channel/cast_channel_api.h

Index: extensions/browser/api/cast_channel/cast_channel_api.h
diff --git a/extensions/browser/api/cast_channel/cast_channel_api.h b/extensions/browser/api/cast_channel/cast_channel_api.h
index 4453a791fab98561da5556b83248c82a5092a864..9be09af3ee55c9968bce7e03d826e355daed2b03 100644
--- a/extensions/browser/api/cast_channel/cast_channel_api.h
+++ b/extensions/browser/api/cast_channel/cast_channel_api.h
@@ -163,11 +163,9 @@ class CastChannelOpenFunction : public CastChannelAsyncApiFunction {
   static net::IPEndPoint* ParseConnectInfo(
       const api::cast_channel::ConnectInfo& connect_info);
 
-  void OnOpen(cast_channel::ChannelError result);
+  void OnOpen(int channel_id, cast_channel::ChannelError result);
 
   std::unique_ptr<api::cast_channel::Open::Params> params_;
-  // The id of the newly opened socket.
-  int new_channel_id_;
   CastChannelAPI* api_;
   std::unique_ptr<net::IPEndPoint> ip_endpoint_;
   base::TimeDelta liveness_timeout_;