Refactor runtime into libraries, better type reps

lib/runtime/dart/math.js

Index: lib/runtime/dart/math.js
diff --git a/lib/runtime/dart/math.js b/lib/runtime/dart/math.js
index bd26b58054e2983e9d7b4ee6c282bb5887dee4a9..309fa3acd5eea4e6007ab08801d101d6c4ebf546 100644
--- a/lib/runtime/dart/math.js
+++ b/lib/runtime/dart/math.js
@@ -1,9 +1,11 @@
-dart.library('dart/math', null, /* Imports */[
+dart_library.library('dart/math', null, /* Imports */[
+  "dart_runtime/dart",
   'dart/core'
 ], /* Lazy imports */[
   'dart/_js_helper'
-], function(exports, core, _js_helper) {
+], function(exports, dart, core, _js_helper) {
   'use strict';
+  let dartx = dart.dartx;
   class _JenkinsSmiHash extends core.Object {
     static combine(hash, value) {
       hash = 536870911 & dart.notNull(hash) + dart.notNull(value);