Enable toolkit_views=1 by default on Mac

build/config/ui.gni

 # Copyright 2014 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.
 
 # This file contains UI-related build flags. It should theoretically be in the
 # src/ui directory and only things that depend on the ui module should get the
 # definitions.
 #
 # However, today we have many "bad" dependencies on some of these flags from,
 # e.g. base, so they need to be global.
@@ skipping 10 matching lines @@
   use_ozone = false
 
   # Support ChromeOS touchpad gestures with ozone.
   use_evdev_gestures = false
 
   # Indicates if Aura is enabled. Aura is a low-level windowing library, sort
   # of a replacement for GDI or GTK.
   use_aura = is_win || is_linux
 
   # True means the UI is built using the "views" framework.
-  toolkit_views = is_win || is_chromeos || use_aura
+  toolkit_views = is_mac || is_win || is_chromeos || use_aura
 
   # Whether we should use glib, a low level C utility library.
   use_glib = is_linux && !use_ozone
 }
 
 # Additional dependent variables -----------------------------------------------
 #
 # These variables depend on other variables and can't be set externally.
 
 if (is_linux && use_glib) {
@@ skipping 11 matching lines @@
 use_default_render_theme = use_aura || is_linux
 
 # Indicates if the UI toolkit depends on X11.
 use_x11 = is_linux && !use_ozone
 
 use_ozone_evdev = use_ozone
 
 use_clipboard_aurax11 = is_linux && use_aura && use_x11
 
 enable_hidpi = is_mac || is_chromeos || is_win