Keep track of when a socket has been destroyed

tests/standalone/io/socket_exception_test.dart

Index: tests/standalone/io/socket_exception_test.dart
diff --git a/tests/standalone/io/socket_exception_test.dart b/tests/standalone/io/socket_exception_test.dart
index 41290d62a32708b0f52e9d259d3c20fbb18f5a83..f882b3e56cc2a6796295aac17a59584c0a56aaf1 100644
--- a/tests/standalone/io/socket_exception_test.dart
+++ b/tests/standalone/io/socket_exception_test.dart
@@ -118,7 +118,7 @@ class SocketExceptionTest {
   static void clientSocketAddDestroyNoErrorTest() {
     ServerSocket.bind("127.0.0.1", 0).then((server) {
       server.listen((socket) {
-        // Passive block data by not sobscribing to socket.
+        // Passive block data by not subscribing to socket.
       });
       Socket.connect("127.0.0.1", server.port).then((client) {
         client.listen((data) {}, onDone: server.close);