Add @JSName annotation for native fields and methods - second try.

tests/compiler/dart2js_native/native_field_rename_1_frog_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.
 
 // A native method prevents other members from having that name, including
 // fields.  However, native fields keep their name.  The implication: a getter
 // for the field must be based on the field's name, not the field's jsname.
 
 class A native "*A" {
   int key;                    //  jsname is 'key'
   int getKey() => key;
 }
 
 class B {
   int key;                    //  jsname is not 'key'
   B([this.key = 222]);
   int getKey() => key;
 }
 
 class X native "*X" {
-  int native_key_method() native 'key';
+  @JSName('key')
+  int native_key_method() native;
   // This should cause B.key to be renamed, but not A.key.
 
-  int key() native 'key';
+  @JSName('key')
+  int key() native;
 }
 
 A makeA() native;
 X makeX() native;
 
 
 void setup() native """
 // This code is all inside 'setup' and so not accesible from the global scope.
 function A(){ this.key = 111; }
 A.prototype.getKey = function(){return this.key;};
@@ skipping 35 matching lines @@
   Expect.equals(111, a.getKey());
   Expect.equals(222, b.getKey());
 }
 
 main() {
   setup();
 
   testTyped();
   testDynamic();
 }