Always mark stdout as blocking when using 'print'.

tests/standalone/io/print_sync_test.dart

Index: tests/standalone/io/print_sync_test.dart
diff --git a/tests/compiler/dart2js/dead_code_test.dart b/tests/standalone/io/print_sync_test.dart
similarity index 50%
copy from tests/compiler/dart2js/dead_code_test.dart
copy to tests/standalone/io/print_sync_test.dart
index e4096c0073ddd5cbfed6d5d94dcff11073e0bb3d..74cc7edcef9c9fafa9319c360f91179c04a15565 100644
--- a/tests/compiler/dart2js/dead_code_test.dart
+++ b/tests/standalone/io/print_sync_test.dart
@@ -2,22 +2,18 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:io';
+
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
-import 'compiler_helper.dart';
-
-String TEST = r'''
-main() {
-  foo(null);
-}
-foo(a) {
-  if (a != null) return 42;
-  return 54;
-}
-''';
 
-main() {
-  asyncTest(() => compileAll(TEST).then((generated) {
-    Expect.isFalse(generated.contains('return 42'), 'dead code not eliminated');
-  }));
+void main() {
+  asyncStart();
+  Process.run(Platform.executable,
+              [Uri.parse(Platform.script)
+                   .resolve('print_sync_script.dart').toString()])
+      .then((out) {
+        asyncEnd();
+        Expect.equals(1002, out.stdout.split('\n').length);
+      });
 }