Fix PWA caption button size on Linux

CC=alancutter
R=pkasting,sky
BUG=911770

Change-Id: I9c591be16ba1c38531834e3cd7e9998c5e3567d8
Reviewed-on: https://chromium-review.googlesource.com/c/1374354
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616157}
5 files changed