Re-land "Format all multitests"

tests/language/dynamic_prefix_core_test.dart

 // Copyright (c) 2012, 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.
 // Test explicit import of dart:core in the source code..
 
 library DynamicPrefixCoreTest.dart;
+
 import "package:expect/expect.dart";
 import "dart:core" as mycore;
 
 void main() {
   // Should still be available because it is not a member of dart:core.
   Expect.isTrue(dynamic is mycore.Type);
 
   Expect.throws(() => mycore.dynamic is mycore.Type, //    //# 01: static type warning
                 (e) => e is mycore.NoSuchMethodError, //   //# 01: continued
                 'dynamic is not a member of dart:core'); //# 01: continued
 }