Ensure CopyElementsImpl is always executed so it fills in holes even if from_size is 0. Allow Fixed…

src/elements.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 678 matching lines @@
       ElementsKind elements_kind = from_holder->GetElementsKind();
       bool is_packed = IsFastPackedElementsKind(elements_kind) &&
           from_holder->IsJSArray();
       if (is_packed) {
         packed_size = Smi::cast(JSArray::cast(from_holder)->length())->value();
         if (copy_size >= 0 && packed_size > copy_size) {
           packed_size = copy_size;
         }
       }
     }
-    if (from->length() == 0 || copy_size == 0) {
-      return from;
-    }
     return ElementsAccessorSubclass::CopyElementsImpl(
         from, from_start, to, to_kind, to_start, packed_size, copy_size);
   }
 
   MUST_USE_RESULT virtual MaybeObject* AddElementsToFixedArray(
       Object* receiver,
       JSObject* holder,
       FixedArray* to,
       FixedArrayBase* from) {
     int len0 = to->length();
@@ skipping 1146 matching lines @@
   if (!maybe_obj->To(&new_backing_store)) return maybe_obj;
   new_backing_store->set(0, length);
   { MaybeObject* result = array->SetContent(new_backing_store);
     if (result->IsFailure()) return result;
   }
   return array;
 }
 
 
 } }  // namespace v8::internal