Make sure builtin functions don't rely on __proto__.

src/d8.js

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 53 matching lines @@
   current = ToInspectableObject(current);
   while (typeof current !== 'undefined') {
     var mirror = new $debug.ObjectMirror(current);
     var properties = mirror.properties();
     for (var i = 0; i < properties.length; i++) {
       var name = properties[i].name();
       if (typeof name === 'string' && name.startsWith(last)) {
         result.push(name);
       }
     }
-    current = ToInspectableObject(current.__proto__);
+    current = ToInspectableObject(Object.getPrototypeOf(current));
   }
   return result;
 }
 
 
 // Global object holding debugger related constants and state.
 var Debug = {};
 
 
 // Debug events which can occour in the V8 JavaScript engine. These originate
@@ skipping 2102 matching lines @@
       json += NumberToJSON_(elem);
     } else if (typeof(elem) === 'string')  {
       json += StringToJSON_(elem);
     } else {
       json += elem;
     }
   }
   json += ']';
   return json;
 }