[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..fd4f1e60af702dc7071f30f8ff24e0827172252d 100644
--- a/src/runtime/runtime-array.cc
+++ b/src/runtime/runtime-array.cc
@@ -206,7 +206,7 @@ RUNTIME_FUNCTION(Runtime_GetArrayKeys) {
     return *isolate->factory()->NewNumberFromUint(Min(actual_length, length));
   }
 
-  KeyAccumulator accumulator(isolate, ALL_PROPERTIES);
+  KeyAccumulator accumulator(isolate, 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);