Add MetalayerMode to the palette.

ash/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/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
 
 # Historical note: Ash shipped on Windows for a couple years to support
@@ skipping 412 matching lines @@
     "system/palette/tools/capture_region_mode.cc",
     "system/palette/tools/capture_region_mode.h",
     "system/palette/tools/capture_screen_action.cc",
     "system/palette/tools/capture_screen_action.h",
     "system/palette/tools/create_note_action.cc",
     "system/palette/tools/create_note_action.h",
     "system/palette/tools/laser_pointer_mode.cc",
     "system/palette/tools/laser_pointer_mode.h",
     "system/palette/tools/magnifier_mode.cc",
     "system/palette/tools/magnifier_mode.h",
+    "system/palette/tools/metalayer_mode.cc",
+    "system/palette/tools/metalayer_mode.h",
     "system/power/battery_notification.cc",
     "system/power/battery_notification.h",
     "system/power/dual_role_notification.cc",
     "system/power/dual_role_notification.h",
     "system/power/power_event_observer.cc",
     "system/power/power_event_observer.h",
     "system/power/power_status.cc",
     "system/power/power_status.h",
     "system/power/power_status_view.cc",
     "system/power/power_status_view.h",
@@ skipping 1048 matching lines @@
     "//content/public/app:both",
     "//device/bluetooth",
   ]
 
   data_deps = [
     "//ash/strings:ash_test_strings",
     "//ash/resources:ash_test_resources_with_content_100_percent",
     "//ash/resources:ash_test_resources_200_percent",
   ]
 }