Picture-in-Picture: remove/rename some methods in player/video element.

Mostly follow-ups from https://chromium-review.googlesource.com/c/chromium/src/+/1379049

Some methods became pointless, some had their meaning significantly
changed.

This CL also changes the timing of requestPictureInPicture() and exitPictureInPicture()
in order to be sync until the call to the service.

Bug: 919860, 930338
Change-Id: I437a060c2dd92021d514c4d6e2ffeb9f4642525b
Reviewed-on: https://chromium-review.googlesource.com/c/1409544
Commit-Queue: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631517}
18 files changed