Use mojo SystemTray interfaces for both mash and classic ash

ash/mus/BUILD.gn

 # Copyright 2015 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/ui.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//services/shell/public/cpp/service.gni")
 import("//services/shell/public/service_manifest.gni")
 import("//tools/grit/repack.gni")
 
@@ skipping 59 matching lines @@
     "screenlock_layout.cc",
     "screenlock_layout.h",
     "shadow.cc",
     "shadow.h",
     "shadow_controller.cc",
     "shadow_controller.h",
     "shelf_delegate_mus.cc",
     "shelf_delegate_mus.h",
     "shell_delegate_mus.cc",
     "shell_delegate_mus.h",
-    "system_tray_delegate_mus.cc",
-    "system_tray_delegate_mus.h",
     "wallpaper_delegate_mus.cc",
     "wallpaper_delegate_mus.h",
     "window_manager.cc",
     "window_manager.h",
     "window_manager_application.cc",
     "window_manager_application.h",
     "window_manager_observer.h",
   ]
 
   defines = [ "NOTIMPLEMENTED_POLICY=5" ]
@@ skipping 173 matching lines @@
     "//ui/views/mus",
   ]
 
   data_deps = [
     ":mus",
     "//mash/quick_launch",
   ]
 
   defines = [ "NOTIMPLEMENTED_POLICY=5" ]
 }