[Media Controls] Keep the overflow menu above the loading animation

This CL adds a z-index to the overflow and text track menus to keep
them above the loading animation.

Bug: 937760
Change-Id: I26e5a5bb6798257dbe1f6aff30b698b72c6801d5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1510493
Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#639103}
1 file changed