[es6] Partially implement Reflect.ownKeys.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 99a8f59046793e78b22b85c70fb7d91f6faaf02c..b2c73630074ae8f0c83dccca4adb814d94fbc1b7 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1779,6 +1779,7 @@ enum AccessorComponent {
 
 enum KeyFilter { SKIP_SYMBOLS, INCLUDE_SYMBOLS };
 
+enum Enumerability { RESPECT_ENUMERABILITY, IGNORE_ENUMERABILITY };
 
 enum GetKeysConversion { KEEP_NUMBERS, CONVERT_TO_STRING };
 
@@ -1926,7 +1927,8 @@ class JSReceiver: public HeapObject {
   MUST_USE_RESULT static MaybeHandle<FixedArray> GetKeys(
       Handle<JSReceiver> object, KeyCollectionType type,
       KeyFilter filter = SKIP_SYMBOLS,
-      GetKeysConversion getConversion = KEEP_NUMBERS);
+      GetKeysConversion getConversion = KEEP_NUMBERS,
+      Enumerability enum_policy = RESPECT_ENUMERABILITY);
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSReceiver);