fixes #168, dart:js implementation with a test

tool/input_sdk/private/js_helper.dart

Index: tool/input_sdk/private/js_helper.dart
diff --git a/tool/input_sdk/private/js_helper.dart b/tool/input_sdk/private/js_helper.dart
index 8dde7a50a49d3e6c4c6e5fd9213280cb835fcdc5..20be8e50285e03dec2bab8c57a9c238311b70bde 100644
--- a/tool/input_sdk/private/js_helper.dart
+++ b/tool/input_sdk/private/js_helper.dart
@@ -594,19 +594,6 @@ fillLiteralMap(keyValuePairs, Map result) {
   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);
 }