Remove deprecated parts of dart:async.

tests/standalone/io/echo_server_stream_test.dart

Index: tests/standalone/io/echo_server_stream_test.dart
diff --git a/tests/standalone/io/echo_server_stream_test.dart b/tests/standalone/io/echo_server_stream_test.dart
index 0684571bc3b496abfb890d2f5266d4d65e4c8c73..2b7615eca737cef672d0244442b294dd7c318443 100644
--- a/tests/standalone/io/echo_server_stream_test.dart
+++ b/tests/standalone/io/echo_server_stream_test.dart
@@ -55,9 +55,8 @@ class EchoServerGame {
       }
     }
 
-    void errorHandler(e) {
+    void errorHandler(e, trace) {
       String msg = "Socket error $e";
-      var trace = getAttachedStackTrace(e);
       if (trace != null) msg += "\nStackTrace: $trace";
       Expect.fail(msg);
     }
@@ -132,9 +131,8 @@ class EchoServer extends TestingServer {
       }
     }
 
-    void errorHandler(e) {
+    void errorHandler(e, trace) {
       String msg = "Socket error $e";
-      var trace = getAttachedStackTrace(e);
       if (trace != null) msg += "\nStackTrace: $trace";
       Expect.fail(msg);
     }