Generate all runtime files from dart.

lib/runtime/dart/_js_helper.js

Index: lib/runtime/dart/_js_helper.js
diff --git a/lib/runtime/dart/_js_helper.js b/lib/runtime/dart/_js_helper.js
index 0c2a3020752c4651e79d70fda4917deef3a65f2d..2a09e5a8f7daa710eef54989f13b530c3f1f2c31 100644
--- a/lib/runtime/dart/_js_helper.js
+++ b/lib/runtime/dart/_js_helper.js
@@ -2,10 +2,11 @@ dart_library.library('dart/_js_helper', null, /* Imports */[
   "dart/_runtime",
   'dart/core',
   'dart/collection',
+  'dart/_utils',
   'dart/_interceptors',
   'dart/_foreign_helper'
 ], /* Lazy imports */[
-], function(exports, dart, core, collection, _interceptors, _foreign_helper) {
+], function(exports, dart, core, collection, utils, _interceptors, _foreign_helper) {
   'use strict';
   let dartx = dart.dartx;
   class NoThrows extends core.Object {
@@ -500,12 +501,12 @@ dart_library.library('dart/_js_helper', null, /* Imports */[
   }
   dart.fn(getRuntimeType, core.Type, [dart.dynamic]);
   function getIndex(array, index) {
-    dart.assert(isJsArray(array));
+    utils.assert(isJsArray(array));
     return array[index];
   }
   dart.fn(getIndex, dart.dynamic, [dart.dynamic, core.int]);
   function getLength(array) {
-    dart.assert(isJsArray(array));
+    utils.assert(isJsArray(array));
     return array.length;
   }
   dart.fn(getLength, core.int, [dart.dynamic]);