Add update available icon in system tray

ash/system/tray/system_tray_controller.cc

Index: ash/system/tray/system_tray_controller.cc
diff --git a/ash/system/tray/system_tray_controller.cc b/ash/system/tray/system_tray_controller.cc
index 5f3d07a08c30ca5d03089df12ab6e0671ea72e11..5dafcceea0d37347bace1e278a854912f02ceea8 100644
--- a/ash/system/tray/system_tray_controller.cc
+++ b/ash/system/tray/system_tray_controller.cc
@@ -70,6 +70,11 @@ void SystemTrayController::ShowIMESettings() {
     system_tray_client_->ShowIMESettings();
 }
 
+void SystemTrayController::ShowAboutChromeOS(bool check_for_update) {
+  if (system_tray_client_)
+    system_tray_client_->ShowAboutChromeOS(check_for_update);
+}
+
 void SystemTrayController::ShowHelp() {
   if (system_tray_client_)
     system_tray_client_->ShowHelp();
@@ -210,4 +215,15 @@ void SystemTrayController::ShowUpdateIcon(mojom::UpdateSeverity severity,
   }
 }
 
+void SystemTrayController::ShowUpdateOverCellularAvailableIcon() {
+  // Show the icon on all displays.
+  for (WmWindow* root : ShellPort::Get()->GetAllRootWindows()) {
+    ash::SystemTray* tray = root->GetRootWindowController()->GetSystemTray();
+    // External monitors might not have a tray yet.
+    if (!tray)
+      continue;
+    tray->tray_update()->ShowUpdateOverCellularAvailableIcon();
+  }
+}
+
 }  // namespace ash