arc: Add icon resource for the notification in migration-skipped session.

chrome/app/vector_icons/BUILD.gn

 # Copyright 2017 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/util/branding.gni")
 import("//ui/vector_icons/vector_icons.gni")
 
 aggregate_vector_icons("chrome_vector_icons") {
   icon_directory = "."
 
@@ skipping 87 matching lines @@
     icons += [
       "default_favicon.icon",
       "google_search_mac_touchbar.icon",
       "new_tab_mac_touchbar.icon",
     ]
   }
 
   if (is_win) {
     icons += [ "open_in_phone.icon" ]
   }
+
+  if (is_chromeos) {
+    icons += [ "arc_migrate_encryption_notification.icon" ]
+  }
 }
 
 source_set("vector_icons") {
   sources = get_target_outputs(":chrome_vector_icons")
   sources += [ "//ui/gfx/vector_icon_types.h" ]
 
   deps = [
     ":chrome_vector_icons",
     "//base",
     "//skia",
   ]
 }