flags: remove media controls flag

This change removes these flags:
  enable-media-controls-expand-gesture
  enable-modern-media-controls
  enable-overflow-icons-for-media-controls
and adds TODOs to remove the backing features.

Bug: None
Change-Id: Ie442b114280c19d5fa89b64d79fa8c92ee7021a8
Reviewed-on: https://chromium-review.googlesource.com/c/1475799
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Becca Hughes <beccahughes@chromium.org>
Auto-Submit: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632779}
5 files changed