Add JSNative utility class with static methods methods to efficiently manipulate typed JSInterop ob…

runtime/bin/builtin.cc

Index: runtime/bin/builtin.cc
diff --git a/runtime/bin/builtin.cc b/runtime/bin/builtin.cc
index c26a76293acf2877e35dc2bdb80a8a8a4e174a63..04fb0600e8742451bd48a7f567c93a52e81313cf 100644
--- a/runtime/bin/builtin.cc
+++ b/runtime/bin/builtin.cc
@@ -24,6 +24,7 @@ Builtin::builtin_lib_props Builtin::builtin_libraries_[] = {
   { "dart:html", html_source_paths_, NULL, NULL, true },
   { "dart:html_common", html_common_source_paths_, NULL, NULL, true},
   { "dart:js", js_source_paths_, NULL, NULL, true},
+  { "dart:js_util", js_util_source_paths_, NULL, NULL, true},
   { "dart:_blink", blink_source_paths_, NULL, NULL, true },
   { "dart:indexed_db", indexeddb_source_paths_, NULL, NULL, true },
   { "cached_patches.dart", cached_patches_source_paths_, NULL, NULL, true },