Add a `@JSExportName` annotation for internal use in the runtime (use it to export dart.assert inst…

lib/runtime/dart/_classes.js

Index: lib/runtime/dart/_classes.js
diff --git a/lib/runtime/dart/_classes.js b/lib/runtime/dart/_classes.js
index 36590277167f0688edaf12a95e590f5ccd14dbd8..837a1da64d7b1d9c592a7fc0cade78760b64d93f 100644
--- a/lib/runtime/dart/_classes.js
+++ b/lib/runtime/dart/_classes.js
@@ -20,7 +20,7 @@ dart_library.library('dart/_classes', null, /* Imports */[
 ], function(exports, dart_utils, core, _interceptors, types, rtti) {
   'use strict';
 
-  const assert = dart_utils.assert_;
+  const assert = dart_utils.assert;
   const copyProperties = dart_utils.copyProperties;
   const copyTheseProperties = dart_utils.copyTheseProperties;
   const defineMemoizedGetter = dart_utils.defineMemoizedGetter;