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

tests/compiler/dart2js_native/native_exception_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.
 
 // Test that dart2js can handle unexpected exception types.
 
 library native_exception_test;
 
 import 'dart:_foreign_helper' show JS;
-
-import "package:expect/expect.dart";
+import 'dart:_js_helper';
+import 'package:expect/expect.dart';
 
 main() {
   var previous;
   check(e) {
     print('$e');
     Expect.equals(e, e);
     Expect.notEquals(e, new Object());
     Expect.notEquals(e, previous);
     previous = e;
     return '$e' != '[object Object]';
   }
   Expect.throws(() { JS('void', 'noGlobalVariableWithThisName'); }, check);
   Expect.throws(() { JS('void', 'throw 3'); }, check);
   Expect.throws(
       () {
         JS('bool', 'Object.prototype.hasOwnProperty.call(undefined, "foo")');
       },
       check);
   Expect.throws(() { JS('void', 'throw new ReferenceError()'); }, check);
   Expect.throws(() { JS('void', 'throw void 0'); }, check);
   Expect.throws(() { JS('void', 'throw "a string"'); }, check);
   Expect.throws(() { JS('void', 'throw null'); }, check);
 }