Revert "[Media Controls] Add Exit Picture-in-Picture button."

This reverts commit f832578e38ffcb735cb1a414ac580ea781b809b9.

Reason for revert: GetOverflowStringName is firing a DCHECK on audio elements. Note that audio elements have the picture-in-picture button (it's just hidden), so the code will need to handle that case

Original change's description:
> [Media Controls] Add Exit Picture-in-Picture button.
> 
> This makes sure clicking the native Picture-in-Picture button (after
> entering Picture-in-Picture) exits Picture-in-Picture and that video
> controls are reflected when entering and exiting Picture-in-Picture.
> 
> Screenshot: https://i.imgur.com/081Xbmb.png
> 
> Bug: 840516, 806249
> Change-Id: I410a4a06cc4eea62dae8e1d368e4d05394f13c86
> Reviewed-on: https://chromium-review.googlesource.com/1084833
> Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
> Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
> Reviewed-by: Jochen Eisinger <jochen@chromium.org>
> Reviewed-by: apacible <apacible@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#564807}

TBR=beaufort.francois@gmail.com,mlamouri@chromium.org,apacible@chromium.org,jochen@chromium.org

Change-Id: Ie6373e9c2e77bb41ac6a5e9a32f59a2b6ce3bf03
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 840516, 806249
Reviewed-on: https://chromium-review.googlesource.com/1089209
Reviewed-by: Tommy Steimel <steimel@chromium.org>
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564971}
16 files changed