Don't allow seal or element property definition on external arrays.

src/runtime.cc

 // Copyright 2011 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 4275 matching lines @@
     // Normalize the elements to enable attributes on the property.
     if (js_object->IsJSGlobalProxy()) {
       // We do not need to do access checks here since these has already
       // been performed by the call to GetOwnProperty.
       Handle<Object> proto(js_object->GetPrototype());
       // If proxy is detached, ignore the assignment. Alternatively,
       // we could throw an exception.
       if (proto->IsNull()) return *obj_value;
       js_object = Handle<JSObject>::cast(proto);
     }
+
+    // Don't allow element properties to be redefined on objects with external
+    // array elements.
+    if (js_object->HasExternalArrayElements()) {
+      Handle<Object> args[2] = { js_object, name };
+      Handle<Object> error =
+          isolate->factory()->NewTypeError("redef_external_array_element",
+                                           HandleVector(args, 2));
+      return isolate->Throw(*error);
+    }
+
     Handle<NumberDictionary> dictionary = NormalizeElements(js_object);
     // Make sure that we never go back to fast case.
     dictionary->set_requires_slow_elements();
     PropertyDetails details = PropertyDetails(attr, NORMAL);
     Handle<NumberDictionary> extended_dictionary =
         NumberDictionarySet(dictionary, index, obj_value, details);
     if (*extended_dictionary != *dictionary) {
       if (js_object->GetElementsKind() == NON_STRICT_ARGUMENTS_ELEMENTS) {
         FixedArray::cast(js_object->elements())->set(1, *extended_dictionary);
       } else {
@@ skipping 8827 matching lines @@
   } else {
     // 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(false);
   }
 }
 
 
 } }  // namespace v8::internal