Move CopyElements to the accessor of the target.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 8328bdc801021c0978442baffae012cde70df566..3e8ef05323e936ba101cff039db63a431b1512f5 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -9306,9 +9306,9 @@ MaybeObject* JSObject::SetFastElementsCapacityAndLength(
     }
   }
   FixedArrayBase* old_elements = elements();
-  ElementsAccessor* accessor = ElementsAccessor::ForKind(elements_kind);
+  ElementsAccessor* accessor = ElementsAccessor::ForKind(new_elements_kind);
   MaybeObject* maybe_obj =
-      accessor->CopyElements(this, new_elements, new_elements_kind);
+      accessor->CopyElements(this, new_elements, elements_kind);
   if (maybe_obj->IsFailure()) return maybe_obj;
 
   if (elements_kind != NON_STRICT_ARGUMENTS_ELEMENTS) {
@@ -9365,9 +9365,9 @@ MaybeObject* JSObject::SetFastDoubleElementsCapacityAndLength(
   }
 
   FixedArrayBase* old_elements = elements();
-  ElementsAccessor* accessor = ElementsAccessor::ForKind(elements_kind);
+  ElementsAccessor* accessor = ElementsAccessor::ForKind(FAST_DOUBLE_ELEMENTS);
   { MaybeObject* maybe_obj =
-        accessor->CopyElements(this, elems, FAST_DOUBLE_ELEMENTS);
+        accessor->CopyElements(this, elems, elements_kind);
     if (maybe_obj->IsFailure()) return maybe_obj;
   }
   if (elements_kind != NON_STRICT_ARGUMENTS_ELEMENTS) {