Re-land "Format all multitests"

tests/language/const_constructor_mixin3_test.dart

Index: tests/language/const_constructor_mixin3_test.dart
diff --git a/tests/language/const_constructor_mixin3_test.dart b/tests/language/const_constructor_mixin3_test.dart
index 0e46fe3c034de63473c17dec8fdf7709ec00bd1c..d92a8acb5ee40719972560a4d6c3e69cfd2602a0 100644
--- a/tests/language/const_constructor_mixin3_test.dart
+++ b/tests/language/const_constructor_mixin3_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();
@@ -11,7 +10,7 @@ class A {
 
 class B extends A
     with Mixin //# 01: compile-time error
-    {
+{
   const B();
 }