fixes #168, dart:js implementation with a test

tool/input_sdk/private/js_helper.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.
 
 library dart._js_helper;
 
 import 'dart:collection';
 
 import 'dart:_foreign_helper' show
     JS,
@@ skipping 576 matching lines @@
   int index = 0;
   int length = getLength(keyValuePairs);
   while (index < length) {
     var key = getIndex(keyValuePairs, index++);
     var value = getIndex(keyValuePairs, index++);
     result[key] = value;
   }
   return result;
 }
 
-/**
- * Called by generated code to convert a Dart closure to a JS
- * closure when the Dart closure is passed to the DOM.
- */
-convertDartClosureToJS(closure, int arity) {
-  // TODO(vsm): Dart2JS wraps closures to:
-  // (a) adjust the calling convention, and
-  // (b) record the source isolate
-  // Do we need either?
-  // See: https://github.com/dart-lang/dev_compiler/issues/164
-  return closure;
-}
-
 bool jsHasOwnProperty(var jsObject, String property) {
   return JS('bool', r'#.hasOwnProperty(#)', jsObject, property);
 }
 
 jsPropertyAccess(var jsObject, String property) {
   return JS('var', r'#[#]', jsObject, property);
 }
 
 /**
  * Called at the end of unaborted switch cases to get the singleton
@@ skipping 149 matching lines @@
 int random64() {
   // TODO(lrn): Use a secure random source.
   int int32a = JS("int", "(Math.random() * 0x100000000) >>> 0");
   int int32b = JS("int", "(Math.random() * 0x100000000) >>> 0");
   return int32a + int32b * 0x100000000;
 }
 
 String jsonEncodeNative(String string) {
   return JS("String", "JSON.stringify(#)", string);
 }