Remove bogus ASSERT, this method can handle ExternalArrays just fine.

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <iomanip>
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
@@ skipping 4258 matching lines @@
   }
 
   return AddDataProperty(&it, value, attributes, STRICT,
                          CERTAINLY_NOT_STORE_FROM_KEYED);
 }
 
 
 MaybeHandle<Object> JSObject::SetOwnElementIgnoreAttributes(
     Handle<JSObject> object, uint32_t index, Handle<Object> value,
     PropertyAttributes attributes, ExecutableAccessorInfoHandling handling) {
-  DCHECK(!object->HasExternalArrayElements());
   Isolate* isolate = object->GetIsolate();
   LookupIterator it(isolate, object, index,
                     LookupIterator::OWN_SKIP_INTERCEPTOR);
   if (it.state() == LookupIterator::ACCESS_CHECK) {
     if (!isolate->MayAccess(object)) {
       return SetPropertyWithFailedAccessCheck(&it, value, STRICT);
     }
     it.Next();
   }
 
@@ skipping 12369 matching lines @@
                                             Handle<Object> new_value) {
   if (cell->value() != *new_value) {
     cell->set_value(*new_value);
     Isolate* isolate = cell->GetIsolate();
     cell->dependent_code()->DeoptimizeDependentCodeGroup(
         isolate, DependentCode::kPropertyCellChangedGroup);
   }
 }
 }  // namespace internal
 }  // namespace v8