[Picture-in-Picture] Add missing [NewObject] to methods in IDL.

Updated spec says IDL for requestPictureInPicture and
exitPictureInPicture should specify that a new object is returned.

https://github.com/WICG/picture-in-picture/pull/76

Bug: 806249
Change-Id: Iba50455ef30c97d87c3e22b9ac95bc4bc41d546d
Reviewed-on: https://chromium-review.googlesource.com/1122226
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/heads/master@{#572257}
2 files changed