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

tests/compiler/dart2js_native/native_call_arity3_frog_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.
 
+import "dart:_js_helper";
 import "package:expect/expect.dart";
 
 // Test similar to NativeCallArity1FrogTest, but with default values to
 // parameters set to null. These parameters should be treated as if they
 // do not have a default value for the native methods.
 
-class A native "A" {
+@Native("A")
+class A {
   int foo(int x) native;
 }
 
-class B native "B" {
+@Native("B")
+class B {
   int foo([x = null, y, z = null]) native;
 }
 
 // TODO(sra): Add a case where the parameters have default values.  Wait until
 // dart:html need non-null default values.
 
 A makeA() native { return new A(); }
 B makeB() native { return new B(); }
 
 void setup() native """
@@ skipping 47 matching lines @@
   Expect.equals(2, b.foo(null, 20));
   Expect.equals(3, b.foo(null, null, 30));
   Expect.throws(() => b.foo(10, 20, 30, 40));
 }
 
 main() {
   setup();
   testDynamicContext();
   testStaticContext();
 }