Add @Native(...) annotation for native class names.

tests/compiler/dart2js_native/issue9182_test.dart

 // Copyright (c) 2013, 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.
 
 // Regression test for Issue 9182.  The generative constructor body function
 // should not have the interceptor calling convention.
 
+import "dart:_js_helper";
 import "package:expect/expect.dart";
 
-class Foo native "A" {
+@Native("A")
+class Foo {
   factory Foo() => makeA();
   // Ensure the instance method 'Bar' uses interceptor convention.
   Bar() => 123;
 }
 
 class Bar {
   var _x, _y;
   // Generative constructor with body, having the same name as interceptor
   // convention instance member.
   Bar(x, y) {
@@ skipping 14 matching lines @@
 
   var things = [new Foo(), new Bar(30, 40)];
   var foo = things[0];
   var bar = things[1];
 
   Expect.equals(123, foo.Bar());  // Ensure that Foo.Bar is used.
 
   Expect.equals(30, bar._x);
   Expect.equals(40, bar._y);
 }