The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/394df2ded0fe41b2930987e77c4b81e67351b20a

commit 394df2ded0fe41b2930987e77c4b81e67351b20a
Author: Scott Chen <scottchen@chromium.org>
Date: Fri Dec 01 15:06:43 2017

MD Extensions: move side-nav outlink to bottom (plus a11y improvements)

This CL does a couple things:
- make the outlink button stay on the bottom of the page
- change the buttons to <a>s for a11y improvement (tabbing, href)

Bug:  787221 ,  788720 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I326b75113a5cbced9ac9ebf5ae58650db63caca0
Reviewed-on: https://chromium-review.googlesource.com/790515
Commit-Queue: Scott Chen <scottchen@chromium.org>
Reviewed-by: Dave Schuyler <dschuyler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#520939}
[modify] https://crrev.com/394df2ded0fe41b2930987e77c4b81e67351b20a/chrome/browser/resources/md_extensions/sidebar.html
[modify] https://crrev.com/394df2ded0fe41b2930987e77c4b81e67351b20a/chrome/browser/resources/md_extensions/sidebar.js