Re-land "Format all multitests"

tests/language/const_switch2_test.dart

 // Copyright (c) 2014, 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:expect/expect.dart';
 
 int main() {
-  var a = [1,2,3][2];
+  var a = [1, 2, 3][2];
   switch (a) {
     case 0.0: //           //# 01: compile-time error
       print("illegal"); // //# 01: continued
     case 1:
       print("OK");
   }
-}
+}