Make sure builtin functions don't rely on __proto__.

src/runtime.cc

 // Copyright 2012 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 949 matching lines @@
       isolate->ReportFailedAccessCheck(JSObject::cast(obj), v8::ACCESS_GET);
       return isolate->heap()->undefined_value();
     }
     obj = obj->GetPrototype(isolate);
   } while (obj->IsJSObject() &&
            JSObject::cast(obj)->map()->is_hidden_prototype());
   return obj;
 }
 
 
+RUNTIME_FUNCTION(MaybeObject*, Runtime_SetPrototype) {
+  NoHandleAllocation ha(isolate);
+  ASSERT(args.length() == 2);
+  CONVERT_ARG_CHECKED(JSReceiver, input_obj, 0);
+  CONVERT_ARG_CHECKED(Object, prototype, 1);
+  return input_obj->SetPrototype(prototype, true);
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_IsInPrototypeChain) {
   NoHandleAllocation ha(isolate);
   ASSERT(args.length() == 2);
   // See ECMA-262, section 15.3.5.3, page 88 (steps 5 - 8).
   Object* O = args[0];
   Object* V = args[1];
   while (true) {
     Object* prototype = V->GetPrototype(isolate);
     if (prototype->IsNull()) return isolate->heap()->false_value();
     if (O == prototype) return isolate->heap()->true_value();
@@ skipping 12321 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal