[proxies] allow duplicate keys for [[OwnPropertyKeys]] trap.

src/runtime/runtime-array.cc

Index: src/runtime/runtime-array.cc
diff --git a/src/runtime/runtime-array.cc b/src/runtime/runtime-array.cc
index 28e92cbd2baa0b8e977609dec2ec14733c6090a2..dacc98470de4fabdb6bb072da3e6aa1024f1a599 100644
--- a/src/runtime/runtime-array.cc
+++ b/src/runtime/runtime-array.cc
@@ -206,7 +206,8 @@ RUNTIME_FUNCTION(Runtime_GetArrayKeys) {
     return *isolate->factory()->NewNumberFromUint(Min(actual_length, length));
   }
 
-  KeyAccumulator accumulator(isolate, ALL_PROPERTIES);
+  KeyAccumulator accumulator(isolate, KeyCollectionType::OWN_ONLY,
+                             ALL_PROPERTIES);
   // No need to separate protoype levels since we only get numbers/element keys
   for (PrototypeIterator iter(isolate, array,
                               PrototypeIterator::START_AT_RECEIVER);