Format all tests.

tests/language/propagate_past_constant_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:expect/expect.dart';
 
 foo(x) => x;
 
 check(y) {
   Expect.equals('foo', y);
 }
 
 main() {
   var x = foo('foo');
   var y = foo(x);
   x = 'constant';
-  check(y); // 'y' should not propagate here unless reference to 'x' is rewritten
+  check(
+      y); // 'y' should not propagate here unless reference to 'x' is rewritten
   foo(x);
   foo(x);
 }