[sync] Add constexpr to EnumSet

components/reading_list/core/reading_list.gni

Index: components/reading_list/core/reading_list.gni
diff --git a/components/reading_list/core/reading_list.gni b/components/reading_list/core/reading_list.gni
deleted file mode 100644
index 26c4e1e7cb59563b3d163fc8ab4ea8c0c47cb4f8..0000000000000000000000000000000000000000
--- a/components/reading_list/core/reading_list.gni
+++ /dev/null
@@ -1,9 +0,0 @@
-# Copyright 2016 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-declare_args() {
-  # Controls whether reading list support is active or not. Currently only
-  # supported on iOS (on other platforms, the feature is always disabled).
-  enable_reading_list = true
-}