Add 'owner' field to sockets, that point to a potential IO resource using that Socket.

sdk/lib/io/secure_server_socket.dart

Index: sdk/lib/io/secure_server_socket.dart
diff --git a/sdk/lib/io/secure_server_socket.dart b/sdk/lib/io/secure_server_socket.dart
index 4b64fe3c01a71e3c63db987999337580cc96d916..e5fa60fe7aaac0026c43c73df771578167f6248f 100644
--- a/sdk/lib/io/secure_server_socket.dart
+++ b/sdk/lib/io/secure_server_socket.dart
@@ -104,6 +104,8 @@ class SecureServerSocket extends Stream<SecureSocket> {
    * is fully closed and is no longer bound.
    */
   Future<SecureServerSocket> close() => _socket.close().then((_) => this);
+
+  void set _owner(owner) { _socket._owner = owner; }
 }
 
 
@@ -278,6 +280,8 @@ class RawSecureServerSocket extends Stream<RawSecureSocket> {
       close();
     }
   }
+
+  void set _owner(owner) { (_socket as dynamic)._owner = owner; }
 }