fixes #168, dart:js implementation with a test

lib/runtime/dart/_foreign_helper.js

 dart_library.library('dart/_foreign_helper', null, /* Imports */[
   "dart_runtime/dart",
   'dart/core'
 ], /* Lazy imports */[
 ], function(exports, dart, core) {
   'use strict';
   let dartx = dart.dartx;
   function JS(typeDescription, codeTemplate, arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7, arg8, arg9, arg10, arg11) {
     if (arg0 === void 0)
       arg0 = null;
@@ skipping 21 matching lines @@
       arg11 = null;
   }
   dart.fn(JS, dart.dynamic, [core.String, core.String], [dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic, dart.dynamic]);
   function JS_CURRENT_ISOLATE_CONTEXT() {
   }
   dart.fn(JS_CURRENT_ISOLATE_CONTEXT, () => dart.definiteFunctionType(IsolateContext, []));
   class IsolateContext extends core.Object {}
   function JS_CALL_IN_ISOLATE(isolate, func) {
   }
   dart.fn(JS_CALL_IN_ISOLATE, dart.dynamic, [dart.dynamic, core.Function]);
-  function DART_CLOSURE_TO_JS(func) {
-  }
-  dart.fn(DART_CLOSURE_TO_JS, dart.dynamic, [core.Function]);
-  function RAW_DART_FUNCTION_REF(func) {
-  }
-  dart.fn(RAW_DART_FUNCTION_REF, dart.dynamic, [core.Function]);
   function JS_SET_CURRENT_ISOLATE(isolate) {
   }
   dart.fn(JS_SET_CURRENT_ISOLATE, dart.void, [dart.dynamic]);
   function JS_CREATE_ISOLATE() {
   }
   dart.fn(JS_CREATE_ISOLATE);
   function JS_DART_OBJECT_CONSTRUCTOR() {
   }
   dart.fn(JS_DART_OBJECT_CONSTRUCTOR);
   function JS_INTERCEPTOR_CONSTANT(type) {
@@ skipping 67 matching lines @@
   });
   function JS_STRING_CONCAT(a, b) {
     return a + b;
   }
   dart.fn(JS_STRING_CONCAT, core.String, [core.String, core.String]);
   // Exports:
   exports.JS = JS;
   exports.JS_CURRENT_ISOLATE_CONTEXT = JS_CURRENT_ISOLATE_CONTEXT;
   exports.IsolateContext = IsolateContext;
   exports.JS_CALL_IN_ISOLATE = JS_CALL_IN_ISOLATE;
-  exports.DART_CLOSURE_TO_JS = DART_CLOSURE_TO_JS;
-  exports.RAW_DART_FUNCTION_REF = RAW_DART_FUNCTION_REF;
   exports.JS_SET_CURRENT_ISOLATE = JS_SET_CURRENT_ISOLATE;
   exports.JS_CREATE_ISOLATE = JS_CREATE_ISOLATE;
   exports.JS_DART_OBJECT_CONSTRUCTOR = JS_DART_OBJECT_CONSTRUCTOR;
   exports.JS_INTERCEPTOR_CONSTANT = JS_INTERCEPTOR_CONSTANT;
   exports.JS_OPERATOR_IS_PREFIX = JS_OPERATOR_IS_PREFIX;
   exports.JS_OPERATOR_AS_PREFIX = JS_OPERATOR_AS_PREFIX;
   exports.JS_OBJECT_CLASS_NAME = JS_OBJECT_CLASS_NAME;
   exports.JS_NULL_CLASS_NAME = JS_NULL_CLASS_NAME;
   exports.JS_FUNCTION_CLASS_NAME = JS_FUNCTION_CLASS_NAME;
   exports.JS_IS_INDEXABLE_FIELD_NAME = JS_IS_INDEXABLE_FIELD_NAME;
   exports.JS_CURRENT_ISOLATE = JS_CURRENT_ISOLATE;
   exports.JS_SIGNATURE_NAME = JS_SIGNATURE_NAME;
   exports.JS_TYPEDEF_TAG = JS_TYPEDEF_TAG;
   exports.JS_FUNCTION_TYPE_TAG = JS_FUNCTION_TYPE_TAG;
   exports.JS_FUNCTION_TYPE_VOID_RETURN_TAG = JS_FUNCTION_TYPE_VOID_RETURN_TAG;
   exports.JS_FUNCTION_TYPE_RETURN_TYPE_TAG = JS_FUNCTION_TYPE_RETURN_TYPE_TAG;
   exports.JS_FUNCTION_TYPE_REQUIRED_PARAMETERS_TAG = JS_FUNCTION_TYPE_REQUIRED_PARAMETERS_TAG;
   exports.JS_FUNCTION_TYPE_OPTIONAL_PARAMETERS_TAG = JS_FUNCTION_TYPE_OPTIONAL_PARAMETERS_TAG;
   exports.JS_FUNCTION_TYPE_NAMED_PARAMETERS_TAG = JS_FUNCTION_TYPE_NAMED_PARAMETERS_TAG;
   exports.JS_GET_NAME = JS_GET_NAME;
   exports.JS_EMBEDDED_GLOBAL = JS_EMBEDDED_GLOBAL;
   exports.JS_GET_FLAG = JS_GET_FLAG;
   exports.JS_EFFECT = JS_EFFECT;
   exports.JS_CONST = JS_CONST;
   exports.JS_STRING_CONCAT = JS_STRING_CONCAT;
 });