[Arguments] Support deletion of arguments properties.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 5443926691023bac454bb0bfd92629d7a9dffee8..d3083ccf3501c9d1933c099db3b1f077cbf1e10d 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1871,6 +1871,13 @@ class JSObject: public HeapObject {
                                                             DeleteMode mode);
   MUST_USE_RESULT MaybeObject* DeleteElementWithInterceptor(uint32_t index);
 
+  // Deletion utilities taking an explicit backing store argument.
+  void DeleteFromFastElements(FixedArray* elements, uint32_t index);
+  MUST_USE_RESULT MaybeObject* DeleteFromDictionaryElements(
+      NumberDictionary* elements,
+      uint32_t index,
+      DeleteMode mode);
+
   PropertyAttributes GetPropertyAttributePostInterceptor(JSObject* receiver,
                                                          String* name,
                                                          bool continue_search);