Use GTK frame button layout when available

BUG=21438
R=erg@chromium.org

Change-Id: I9c596a297a48ab7b4405fbe13b99ddede99c5d54
Reviewed-on: https://chromium-review.googlesource.com/629317
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Elliot Glaysher <erg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#497169}
10 files changed