Refactor runtime into libraries, better type reps

test/codegen/expect/domtest.js

Index: test/codegen/expect/domtest.js
diff --git a/test/codegen/expect/domtest.js b/test/codegen/expect/domtest.js
index 767f1482ea304a61e9b4eb62aaa391a0ded67e35..aad27627901b6530ea858207e6e99698efb02598 100644
--- a/test/codegen/expect/domtest.js
+++ b/test/codegen/expect/domtest.js
@@ -1,9 +1,11 @@
-dart.library('domtest', null, /* Imports */[
+dart_library.library('domtest', null, /* Imports */[
+  "dart_runtime/dart",
   'sunflower/dom',
   'dart/core'
 ], /* Lazy imports */[
-], function(exports, dom, core) {
+], function(exports, dart, dom, core) {
   'use strict';
+  let dartx = dart.dartx;
   function testNativeIndexers() {
     let nodes = dom.document.querySelector('body').childNodes;
     for (let i = 0; dart.notNull(i) < dart.notNull(nodes.length); i = dart.notNull(i) + 1) {