Add missing copyright on test cases.

pkg/front_end/testcases/micro.dart

+// Copyright (c) 2017, 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.
+
 staticMethod() {
   return "sdfg";
 }
 
 class Foo {
   instanceMethod() {
     return 123;
   }
 }
 
@@ skipping 54 matching lines @@
 
   var subBox = new SubFinalBox("dfg");
   var c = subBox.finalField;
 
   makeDynamicCall(new DynamicReceiver1());
   makeDynamicCall(new DynamicReceiver2());
 
   var list = ["string"];
   var d = list[0];
 }