Merge pull request #972 from dart-lang/srawlins-patch-2

Remove unused dart:async imports.
diff --git a/test/io_test.dart b/test/io_test.dart
index 57f1dcc..00aae58 100644
--- a/test/io_test.dart
+++ b/test/io_test.dart
@@ -4,7 +4,6 @@
 
 library dart_style.test.io;
 
-import 'dart:async';
 import 'dart:io';
 
 import 'package:dart_style/src/io.dart';