Switch Js to JS

tests/html/js_dart_to_string_test.dart

 // Copyright (c) 2015, 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.
 
-@Js()
+@JS()
 library js_typed_interop_test;
 
 import 'dart:html';
 
 import 'package:js/js.dart';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 
 _injectJs() {
   document.body.append(new ScriptElement()
     ..type = 'text/javascript'
     ..innerHtml = r"""
 
   function jsToStringViaCoercion(a) {
     return a + '';
   };
 """);
 }
 
-@Js()
+@JS()
 external String jsToStringViaCoercion(obj);
 
 class ExampleClassWithCustomToString {
   var x;
   ExampleClassWithCustomToString(this.x);
   String toString() => "#$x#";
 }
 
 main() {
   _injectJs();
 
   useHtmlConfiguration();
 
   group('toString', () {
     test('custom dart', () {
       var x = new ExampleClassWithCustomToString("fooBar");
       expect(jsToStringViaCoercion(x), equals("#fooBar#"));
       expect(jsToStringViaCoercion({'a' : 1, 'b': 2}), equals("{a: 1, b: 2}"));
     });
   });
 }