MacViews: Consolidate flags. Just use --secondary-ui-md to enable MacViews.

chrome/browser/ui/BUILD.gn

 # 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.
 
 import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//build/split_static_library.gni")
 import("//chrome/common/features.gni")
@@ skipping 1411 matching lines @@
     ]
   } else {  # Not ash.
     sources += [ "views/touch_uma/touch_uma.cc" ]
   }
   if (toolkit_views) {
     sources += [
       "autofill/save_card_bubble_controller.h",
       "autofill/save_card_bubble_controller_impl.cc",
       "autofill/save_card_bubble_controller_impl.h",
       "autofill/save_card_bubble_view.h",
-      "browser_dialogs_mac.cc",
       "views/apps/app_info_dialog/app_info_dialog_container.cc",
       "views/apps/app_info_dialog/app_info_dialog_container.h",
       "views/apps/app_info_dialog/app_info_dialog_views.cc",
       "views/apps/app_info_dialog/app_info_dialog_views.h",
       "views/apps/app_info_dialog/app_info_footer_panel.cc",
       "views/apps/app_info_dialog/app_info_footer_panel.h",
       "views/apps/app_info_dialog/app_info_header_panel.cc",
       "views/apps/app_info_dialog/app_info_header_panel.h",
       "views/apps/app_info_dialog/app_info_panel.cc",
       "views/apps/app_info_dialog/app_info_panel.h",
@@ skipping 2037 matching lines @@
       "test/test_confirm_bubble_model.cc",
       "test/test_confirm_bubble_model.h",
     ]
     deps += [ "//chrome/test:test_support_ui" ]
   }
 
   if (enable_extensions) {
     deps += [ "//extensions/browser" ]
   }
 }