[Picture-in-Picture] Add disablePictureInPicture video attribute

This is still incomplete as it still needs to reject pending requestPiP promises.

Bug: 806249
Change-Id: I256cf5fa092e4e03a7a82135761e2160fbdba043
Reviewed-on: https://chromium-review.googlesource.com/891958
Reviewed-by: Mike West <mkwst@chromium.org>
Reviewed-by: Mounir Lamouri (slow) <mlamouri@chromium.org>
Commit-Queue: Mounir Lamouri (slow) <mlamouri@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533674}
12 files changed