[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 0a50bb8b7fad054a157dcb67f4e12ac95fb399f3..8bb0158a2e96446fc5d7e6167c070481a6fd1212 100644
--- a/extensions/browser/api/cast_channel/cast_channel_api.h
+++ b/extensions/browser/api/cast_channel/cast_channel_api.h
@@ -174,11 +174,9 @@ 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_;
   cast_channel::ChannelAuthType channel_auth_;