Fix JSON.stringify wrt harmony proxies.

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 9170 matching lines @@
   }
 }
 
 
 // Push an object unto an array of objects if it is not already in the
 // array.  Returns true if the element was pushed on the stack and
 // false otherwise.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_PushIfAbsent) {
   ASSERT(args.length() == 2);
   CONVERT_ARG_CHECKED(JSArray, array, 0);
-  CONVERT_ARG_CHECKED(JSObject, element, 1);
+  CONVERT_ARG_CHECKED(JSReceiver, element, 1);
   RUNTIME_ASSERT(array->HasFastSmiOrObjectElements());
   int length = Smi::cast(array->length())->value();
   FixedArray* elements = FixedArray::cast(array->elements());
   for (int i = 0; i < length; i++) {
     if (elements->get(i) == element) return isolate->heap()->false_value();
   }
   Object* obj;
   // Strict not needed. Used for cycle detection in Array join implementation.
   { MaybeObject* maybe_obj =
         array->SetFastElement(length, element, kNonStrictMode, true);
@@ skipping 4099 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