Add update available icon in system tray

chrome/browser/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/chrome_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 3636 matching lines @@
       "themes/theme_properties.cc",
       "themes/theme_service.cc",
       "themes/theme_service.h",
       "themes/theme_service_factory.cc",
       "themes/theme_service_factory.h",
       "themes/theme_service_mac.mm",
       "themes/theme_syncable_service.cc",
       "themes/theme_syncable_service.h",
       "upgrade_detector.cc",
       "upgrade_detector.h",
+      "upgrade_observer.h",
       "usb/usb_chooser_controller.cc",
       "usb/usb_chooser_controller.h",
       "usb/web_usb_chooser_service.cc",
       "usb/web_usb_chooser_service.h",
       "usb/web_usb_detector.cc",
       "usb/web_usb_detector.h",
     ]
     deps += [
       ":theme_properties",
       "//apps",
@@ skipping 1081 matching lines @@
       "media/pepper_cdm_test_constants.cc",
       "media/pepper_cdm_test_constants.h",
     ]
   }
 }
 
 service_manifest("preferences_forwarder_manifest") {
   name = "preferences_forwarder"
   source = "prefs/forwarder_manifest.json"
 }