Kill NOTIFICATION_EXTENSION_UNLOADED_DEPRECATED

There's no place where NOTIFICATION_EXTENSION_UNLOADED_DEPRECATED is observed.

BUG=411568

Review-Url: https://codereview.chromium.org/2824673002
Cr-Commit-Position: refs/heads/master@{#466951}
diff --git a/chrome/browser/themes/theme_service.cc b/chrome/browser/themes/theme_service.cc
index 402ab6e..425d762 100644
--- a/chrome/browser/themes/theme_service.cc
+++ b/chrome/browser/themes/theme_service.cc
@@ -547,7 +547,7 @@
   // There should be no more infobars. This may not be the case because of
   // http://crbug.com/62154
   // RemoveUnusedThemes is called on a task because ClearAllThemeData() may
-  // be called as a result of NOTIFICATION_EXTENSION_UNLOADED_DEPRECATED.
+  // be called as a result of OnExtensionUnloaded().
   base::ThreadTaskRunnerHandle::Get()->PostTask(
       FROM_HERE, base::Bind(&ThemeService::RemoveUnusedThemes,
                             weak_ptr_factory_.GetWeakPtr(), true));