Re-land "Format all multitests"

tests/language/const_constructor_mixin_test.dart

Index: tests/language/const_constructor_mixin_test.dart
diff --git a/tests/language/const_constructor_mixin_test.dart b/tests/language/const_constructor_mixin_test.dart
index 29664b5a3287dee3146b12fc033f75b3024bbb88..58dc68fb9ae9276826fdd596f9179881102f943a 100644
--- a/tests/language/const_constructor_mixin_test.dart
+++ b/tests/language/const_constructor_mixin_test.dart
@@ -2,8 +2,7 @@
 // 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.
 
-class Mixin {
-}
+class Mixin {}
 
 class A {
   const A(foo);
@@ -11,7 +10,7 @@ class A {
 
 class B extends A
     with Mixin // //# 01: compile-time error
-    {
+{
   const B(foo) : super(foo);
 }