Delete dart2js specific private library code

tool/input_sdk/private/native_helper.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.
 
 part of _js_helper;
 
 
-// TODO(ngeoffray): stop using this method once our optimizers can
-// change str1.contains(str2) into str1.indexOf(str2) != -1.
-bool contains(String userAgent, String name) {
-  return JS('int', '#.indexOf(#)', userAgent, name) != -1;
-}
-
-int arrayLength(List array) {
-  return JS('int', '#.length', array);
-}
-
-arrayGet(List array, int index) {
-  return JS('var', '#[#]', array, index);
-}
-
-void arraySet(List array, int index, var value) {
-  JS('var', '#[#] = #', array, index, value);
-}
-
-propertyGet(var object, String property) {
-  return JS('var', '#[#]', object, property);
-}
-
-bool callHasOwnProperty(var function, var object, String property) {
-  return JS('bool', '#.call(#, #)', function, object, property);
-}
-
-void propertySet(var object, String property, var value) {
-  JS('var', '#[#] = #', object, property, value);
-}
-
-getPropertyFromPrototype(var object, String name) {
-  return JS('var', 'Object.getPrototypeOf(#)[#]', object, name);
-}
-
 /**
  * Sets a JavaScript property on an object.
  */
 void defineProperty(var obj, String property, var value) {
   JS('void',
       'Object.defineProperty(#, #, '
           '{value: #, enumerable: false, writable: true, configurable: true})',
       obj,
       property,
       value);
 }