[bootstrapper] extra natives must not use natives syntax.

test/cctest/test-extra.js

Index: test/cctest/test-extra.js
diff --git a/test/cctest/test-extra.js b/test/cctest/test-extra.js
index dfb6c8012cdbfad93b894acb7dbab6b63c714af4..b3752d97b28d96b38ca97b71739d0e139bee8eef 100644
--- a/test/cctest/test-extra.js
+++ b/test/cctest/test-extra.js
@@ -12,6 +12,15 @@
     return binding.runtime(3);
   };
 
+  binding.testFunctionToString = function() {
+    function foo() { return 1; }
+    return foo.toString();
+  };
+
+  binding.testStackTrace = function(f) {
+    return f();
+  }
+
   // Exercise all of the extras utils:
   // - v8.createPrivateSymbol
   // - v8.simpleBind, v8.uncurryThis