Format all tests.

tests/language_strong/mixin_abstract_getter_test.dart

 // Copyright (c) 2016, 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';
 
 abstract class B {
   int get x;
 }
 
 class C {
   int get x => 42;
 }
 
 class D extends C with B {
   final int x;
 
   D(this.x);
 }
 
-
 class C2 {
   int get x => 42;
 }
 
 abstract class B2 extends C2 {
   int get x;
 }
 
 class D2 extends B2 {
   final int x;
 
   D2(this.x);
 }
 
-
 void main() {
   var d = new D(17);
   Expect.equals(d.x, 17);
 
   var d2 = new D2(17);
   Expect.equals(d.x, 17);
 }