Implementing "real" realtime update is technically difficult and consumes CPU.

mcirimele@ proposed to reload directory contents when Files app gets focus, which sounds practical. We will try this method first.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/84fee0ebfe570813c04f6b759bf415b214fb1aad

commit 84fee0ebfe570813c04f6b759bf415b214fb1aad
Author: Shuhei Takahashi <nya@chromium.org>
Date: Tue Sep 26 03:00:39 2017

recent: Refresh directory contents when the window gets focus.

Recent root is not watchable but there is no refresh button today. In
order to refresh, the user needs to change the current directory to
another file system, and then go back to Recent root, which is not
awesome.

This change lets Recent root to silently refresh when Files app window
gets focus.

Bug:  758622 
Test: Manually test the contents refresh on focusing Files app window
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ie36c8ec8885567f555d273c3b6d876450a8eb492
Reviewed-on: https://chromium-review.googlesource.com/680678
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Commit-Queue: Shuhei Takahashi <nya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#504268}
[modify] https://crrev.com/84fee0ebfe570813c04f6b759bf415b214fb1aad/ui/file_manager/file_manager/foreground/js/main_window_component.js