GitLab

Allow Chrome users on platform that do not have system caption
styling to provide a default styling for WebVTT captions displayed
by Blink. This should affect Chrome OS and Linux as Windows, macOS
and Android have system settings.

Design doc: https://docs.google.com/document/d/1wgKMbvP8nJkUKXkwnh5iEajSa4GHxDURL8kHIyHEO4s/edit?hl=en#

Bug: 976966
Change-Id: I41282753305b81f76e6b3f565516160cd63d69f9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1656714Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Esmael El-Moslimany <aee@chromium.org>
Commit-Queue: Evan Liu <evliu@google.com>
Cr-Commit-Position: refs/heads/master@{#672706}