Support unary - operator.

dart/tests/compiler/dart2js/mirrors_helper.dart

 // Copyright (c) 2012, 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.
 
 /**
  * This file is read by 'mirrors_test.dart'.
  */
 
 #library('mirrors_helper');
 
@@ skipping 14 matching lines @@
 class Baz<E,F extends Foo> implements Bar<E> {
   Baz();
   const Baz.named();
   factory Baz.factory() => new Baz<E,F>();
 
   static method1(e) {}
   void method2(E e, [F f = null]) {}
   Baz<E,F> method3(E func1(F f), Func<E,F> func2) => null;
 
   bool operator==(Object other) => false;
-  int operator negate() => 0;
+  int operator-() => 0;
 }
 
 class Boz extends Foo {
   var field1;
   int _field2;
   final String field3 = "field3";
 
   int get field2() => _field2;
   void set field2(int value) {
     _field2 = value;
   }
 }