dart2js: run dartfmt on tests

tests/compiler/dart2js_extra/lookup_map/dead_entry_single_nested_pairs_test.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // 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 'package:lookup_map/lookup_map.dart';
 import 'package:expect/expect.dart';
-class A{}
-class B{}
+
+class A {}
+
+class B {}
+
 const map = const LookupMap(const [], const [
-    const LookupMap.pair(A, "the-text-for-A"),
-    const LookupMap.pair(B, "the-text-for-B"),
+  const LookupMap.pair(A, "the-text-for-A"),
+  const LookupMap.pair(B, "the-text-for-B"),
 ]);
 
 main() {
   Expect.equals(map[A], "the-text-for-A");
 }