GitLab

Make the initialization promise await DOMContentLoaded and then apply
i18n transforms to the video player DOM [1].

Minor: correct commentary, add commentary. Add assertions re document
readyState when the i18n template strings are applied.

[1] Applying i18n strings to an incomplete (readyState === 'loading')
DOM document makes no sense at all.

Test: browser_tests --gtest_filter="VideoPlayerBrowserTest*"
Bug: 884963
Change-Id: Ie5a25763c54c56e949edde40c7e06b8eaad230c4
Reviewed-on: https://chromium-review.googlesource.com/1233394
Commit-Queue: Noel Gordon <noel@chromium.org>
Reviewed-by: Trent Apted <tapted@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592690}