Fix and improve isolate tests.

tests/isolate/global_error_handler_stream_test.dart

Index: tests/isolate/global_error_handler_stream_test.dart
diff --git a/tests/isolate/global_error_handler_stream_test.dart b/tests/isolate/global_error_handler_stream_test.dart
index 14f2cbbcd1eae420935b8321a5d6fced990133d1..5c094872b0f6936228625f5de89dd505dba68696 100644
--- a/tests/isolate/global_error_handler_stream_test.dart
+++ b/tests/isolate/global_error_handler_stream_test.dart
@@ -21,7 +21,7 @@ void runFunctions() {
 
 void startTest(StreamSink finishSink) {
   firstFunction = () { throw new RuntimeError("ignore exception"); };
-  finishFunction = () { finishSink.add("done"); finishPort.close(); };
+  finishFunction = () { finishSink.add("done"); finishSink.close(); };
   new Timer(Duration.ZERO, runFunctions);
 }