Stop using the Hashable interface.

tests/compiler/dart2js_foreign/native_method_rename2_test.dart

 // Copyright (c) 2011, 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.
 
 // Test the feature where the native string declares the native method's name.
 
 @native("*A")
-class A  {
+class A {
   @native('fooA')
   int foo();
 }
 
 @native("*B")
 class B extends A  {
   @native('fooB')
   int foo();
 }
 
@@ skipping 56 matching lines @@
 expectNoSuchMethod(action, note) {
   bool caught = false;
   try {
     action();
   } catch (ex) {
     caught = true;
     Expect.isTrue(ex is NoSuchMethodError, note);
   }
   Expect.isTrue(caught, note);
 }