Revert of ash: Use system tray mojo interface to show system update tray icon

ash/common/system/tray/default_system_tray_delegate.cc

Index: ash/common/system/tray/default_system_tray_delegate.cc
diff --git a/ash/common/system/tray/default_system_tray_delegate.cc b/ash/common/system/tray/default_system_tray_delegate.cc
index 91f3a3306ce8a16773c13260e63d1e63d3587bfe..7c140544e823922f6871a4991839165a435e79ba 100644
--- a/ash/common/system/tray/default_system_tray_delegate.cc
+++ b/ash/common/system/tray/default_system_tray_delegate.cc
@@ -5,6 +5,11 @@
 #include "ash/common/system/tray/default_system_tray_delegate.h"
 
 #include <string>
+#include <utility>
+
+#include "ash/common/system/networking_config_delegate.h"
+#include "base/message_loop/message_loop.h"
+#include "base/time/time.h"
 
 namespace ash {
 
@@ -25,6 +30,13 @@
 
 bool DefaultSystemTrayDelegate::IsUserSupervised() const {
   return GetUserLoginStatus() == LoginStatus::SUPERVISED;
+}
+
+void DefaultSystemTrayDelegate::GetSystemUpdateInfo(UpdateInfo* info) const {
+  DCHECK(info);
+  info->severity = UpdateInfo::UPDATE_NONE;
+  info->update_required = true;
+  info->factory_reset_required = false;
 }
 
 bool DefaultSystemTrayDelegate::ShouldShowSettings() const {