The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0c4b5a0a07df8a078ae2b6f622b405a5358f164f

commit 0c4b5a0a07df8a078ae2b6f622b405a5358f164f
Author: Dominik Röttsches <drott@chromium.org>
Date: Thu Apr 19 16:32:43 2018

Remove mac OS 10.9 specific font workarounds

After the mac OS 10.9 deprecation in crbug.com/806071 remove old font
code workarounds in Blink platform code.

Bug:  834776 
Change-Id: Ia3559a233e3e50f59f6db7d1cb42e4b8d5be1960
Reviewed-on: https://chromium-review.googlesource.com/1019405
Commit-Queue: Dominik Röttsches <drott@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552043}
[modify] https://crrev.com/0c4b5a0a07df8a078ae2b6f622b405a5358f164f/third_party/blink/renderer/core/layout/layout_theme_mac.h
[modify] https://crrev.com/0c4b5a0a07df8a078ae2b6f622b405a5358f164f/third_party/blink/renderer/core/layout/layout_theme_mac.mm
[modify] https://crrev.com/0c4b5a0a07df8a078ae2b6f622b405a5358f164f/third_party/blink/renderer/platform/fonts/mac/font_family_matcher_mac.mm
[modify] https://crrev.com/0c4b5a0a07df8a078ae2b6f622b405a5358f164f/third_party/blink/renderer/platform/mac/version_util_mac.h
[modify] https://crrev.com/0c4b5a0a07df8a078ae2b6f622b405a5358f164f/third_party/blink/renderer/platform/mac/version_util_mac_test.mm

> @behdad: Should we remove 10.9 specific things in HarfBuzz as well?

We recently merged a patch to allow compiling it on 10.5 with Astsui!  I don't like that, but apparently there are people who still compile it there. So, probably not so fast yet.

> [...] Atsui

Wow, okay :) Thanks for the quick reply.