Stop using the Hashable interface.

tests/compiler/dart2js_foreign/native_no_such_method_exception_test.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.
 
 @native("*A")
-class A  {
+class A {
   bar() => 42;
 }
 
 @native("*B")
-class B  {
+class B {
   foo() => 42;
 }
 
 @native makeA();
 
 @native("""
   function A() {}
   makeA = function() { return new A; }
 """)
 setup();
 
 main() {
   setup();
   var a = makeA();
   a.bar();
   var exception;
   try {
     a.foo();
   } on NoSuchMethodError catch (e) {
     exception = e;
   }
   Expect.isNotNull(exception);
 }