dart2js: add compiler builtins to the core-runtime.

sdk/lib/_internal/compiler/js_lib/native_helper.dart

Index: sdk/lib/_internal/compiler/js_lib/native_helper.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/native_helper.dart b/sdk/lib/_internal/compiler/js_lib/native_helper.dart
index bec5bbae9b95df632c4e2979cfb295b7c18b199c..82f97f5f002d2154a7bd0281b0563c140e8dbec6 100644
--- a/sdk/lib/_internal/compiler/js_lib/native_helper.dart
+++ b/sdk/lib/_internal/compiler/js_lib/native_helper.dart
@@ -91,7 +91,10 @@ void defineProperty(var obj, String property, var value) {
 // Is [obj] an instance of a Dart-defined class?
 bool isDartObject(obj) {
   // Some of the extra parens here are necessary.

[sra1, 2015/04/14 21:02:01]

Parens should no longer be needed, but do no harm.

[floitsch, 2015/04/15 14:34:36]

Acknowledged.

-  return JS('bool', '((#) instanceof (#))', obj, JS_DART_OBJECT_CONSTRUCTOR());
+  return JS('bool', '((#) instanceof (#))',
+      obj,
+      JS_BUILTIN('depends:none;effects:none;',
+                 JsBuiltin.dartObjectConstructor));
 }
 
 /**