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

ash/common/system/update/tray_update.h

Index: ash/common/system/update/tray_update.h
diff --git a/ash/common/system/update/tray_update.h b/ash/common/system/update/tray_update.h
index 3850804bc888a2ba3efca6e12f41ecdae7475540..5cf23f7002701f4e9837b28117fe9aaf4a2c23b5 100644
--- a/ash/common/system/update/tray_update.h
+++ b/ash/common/system/update/tray_update.h
@@ -7,6 +7,7 @@
 
 #include "ash/ash_export.h"
 #include "ash/common/system/tray/tray_image_item.h"
+#include "ash/common/system/update/update_observer.h"
 #include "base/macros.h"
 
 namespace views {
@@ -15,37 +16,19 @@
 
 namespace ash {
 
-namespace mojom {
-enum class UpdateSeverity;
-}
-
-// The system update tray item. The tray icon stays visible once an update
-// notification is received. The icon only disappears after a reboot to apply
-// the update. Exported for test.
-class ASH_EXPORT TrayUpdate : public TrayImageItem {
+// The system update tray item. Exported for test.
+class ASH_EXPORT TrayUpdate : public TrayImageItem, public UpdateObserver {
  public:
   explicit TrayUpdate(SystemTray* system_tray);
   ~TrayUpdate() override;
 
-  // Shows an icon in the system tray indicating that a software update is
-  // available. Once shown the icon persists until reboot. |severity| and
-  // |factory_reset_required| are used to set the icon, color, and tooltip.
-  void ShowUpdateIcon(mojom::UpdateSeverity severity,
-                      bool factory_reset_required);
-
  private:
-  class UpdateView;
-
   // Overridden from TrayImageItem.
   bool GetInitialVisibility() override;
   views::View* CreateDefaultView(LoginStatus status) override;
 
-  // If an external monitor is connected then the system tray may be created
-  // after the update data is sent from chrome, so share the update info between
-  // all instances.
-  static bool update_required_;
-  static mojom::UpdateSeverity severity_;
-  static bool factory_reset_required_;
+  // Overridden from UpdateObserver.
+  void OnUpdateRecommended(const UpdateInfo& info) override;
 
   DISALLOW_COPY_AND_ASSIGN(TrayUpdate);
 };