[CrOS Video Player] Change to ES6 class and arrow annotation. Add missing dependencies and type check.

Bug: 909963
Change-Id: Ie024a155e423ea05e81e389c4de7c7ab57564a8e
Reviewed-on: https://chromium-review.googlesource.com/c/1474800
Reviewed-by: Trent Apted <tapted@chromium.org>
Commit-Queue: Jazz Xu <jazzhsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632881}
2 files changed