Convert ui/views_content_client away from base::Bind/base::Callback

base::Bind/base::Callback are deprecated in favor of either
base::BindOnce/base::OnceCallback or base::BindRepeating/
base::RepeatingCallback (depending on whether the callback
is invoked once or multiple time).

Convert all references to base::Bind/base::Callback in
ui/views_content_client to the recommended methods/types
(only references found were in comments).

Bug: 1007854
Change-Id: I5a59a9dcf93665dcdddb55edda06b4a166bd6448
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1829103
Commit-Queue: Trent Apted <tapted@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700954}

ui/views_content_client/views_content_client.h

@@ -40,7 +40,8 @@ namespace ui {
 //   ui::ViewsContentClient params(argc, argv);
 // #endif
 //
-//   params.set_task(base::Bind(&InitMyApp));
+//   params.set_on_pre_main_message_loop_run_callback(
+//       base::BindOnce(&InitMyApp));
 //   return params.RunMain();
 // }
 class VIEWS_CONTENT_CLIENT_EXPORT ViewsContentClient {