Add a row in the network tray to inform users to turn Bluetooth on to enable Tether.

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 520 matching lines @@
     "system/tray/tray_constants.cc",
     "system/tray/tray_constants.h",
     "system/tray/tray_container.cc",
     "system/tray/tray_container.h",
     "system/tray/tray_details_view.cc",
     "system/tray/tray_details_view.h",
     "system/tray/tray_event_filter.cc",
     "system/tray/tray_event_filter.h",
     "system/tray/tray_image_item.cc",
     "system/tray/tray_image_item.h",
+    "system/tray/tray_info_label.cc",
+    "system/tray/tray_info_label.h",
     "system/tray/tray_item_more.cc",
     "system/tray/tray_item_more.h",
     "system/tray/tray_item_view.cc",
     "system/tray/tray_item_view.h",
     "system/tray/tray_popup_header_button.cc",
     "system/tray/tray_popup_header_button.h",
     "system/tray/tray_popup_ink_drop_style.h",
     "system/tray/tray_popup_item_style.cc",
     "system/tray/tray_popup_item_style.h",
     "system/tray/tray_popup_utils.cc",
@@ skipping 689 matching lines @@
     "system/session/logout_confirmation_controller_unittest.cc",
     "system/session/tray_session_length_limit_unittest.cc",
     "system/status_area_widget_unittest.cc",
     "system/supervised/tray_supervised_user_unittest.cc",
     "system/tiles/tray_tiles_unittest.cc",
     "system/toast/toast_manager_unittest.cc",
     "system/tray/size_range_layout_unittest.cc",
     "system/tray/system_tray_unittest.cc",
     "system/tray/tray_details_view_unittest.cc",
     "system/tray/tray_event_filter_unittest.cc",
+    "system/tray/tray_info_label_unittest.cc",
     "system/tray/tri_view_unittest.cc",
     "system/tray_tracing_unittest.cc",
     "system/update/tray_update_unittest.cc",
     "system/user/tray_user_unittest.cc",
     "system/web_notification/ash_popup_alignment_delegate_unittest.cc",
     "system/web_notification/web_notification_tray_unittest.cc",
     "test/ash_test_helper_unittest.cc",
     "tooltips/tooltip_controller_unittest.cc",
     "tray_action/tray_action_unittest.cc",
     "wallpaper/wallpaper_controller_unittest.cc",
@@ skipping 516 matching lines @@
   deps = [
     ":test_support_with_content",
     "//base",
     "//skia",
     "//testing/gtest",
     "//ui/aura",
     "//ui/base",
     "//ui/gl:test_support",
   ]
 }