Revert "Add Skip Ad button to Picture-in-Picture window."

This reverts commit b0281b1250cdec351658e9bf07dd5f5d3331ef91.

Reason for revert: Broke build (see https://ci.chromium.org/buildbot/chromium.chrome/Google%20Chrome%20ChromeOS/60556 )

Original change's description:
> Add Skip Ad button to Picture-in-Picture window.
> 
> This CL adds 'skipad' to the Media Session actions available to web
> developers. It allows them to use it to show/hide a Skip Ad button in
> the Picture-in-Picture window. When users clicks it, the action handler
> is called.
> 
> Screenshots: https://imgur.com/a/fxBNTKf
> 
> Change-Id: I017421e2efe9a8b31fd577647c1e2b5f73cb23f0
> Bug: 910436
> Reviewed-on: https://chromium-review.googlesource.com/c/1393331
> Reviewed-by: Daniel Cheng <dcheng@chromium.org>
> Reviewed-by: Jochen Eisinger <jochen@chromium.org>
> Reviewed-by: Becca Hughes <beccahughes@chromium.org>
> Reviewed-by: Eliot Courtney <edcourtney@chromium.org>
> Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
> Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
> Cr-Commit-Position: refs/heads/master@{#622306}

TBR=dcheng@chromium.org,beaufort.francois@gmail.com,mlamouri@chromium.org,jochen@chromium.org,edcourtney@chromium.org,beccahughes@chromium.org

Change-Id: I2d02199072a3d8f1fc173c74ad7be4203f4506c8
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 910436
Reviewed-on: https://chromium-review.googlesource.com/c/1408269
Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Commit-Queue: Roman Sorokin [CET] <rsorokin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622308}
31 files changed