[Picture-in-Picture] Reject temporarily if video src is a MediaStream.

This CL makses sure requestPictureInPicture promise rejects whem video
src is a MediaStream as backend is not implemented yet. This will remove
confusion during upcoming Origin Trial.

Bug: 806249
Change-Id: I65506111f256b9b0684bdd7d179d01d81e0974a0
Reviewed-on: https://chromium-review.googlesource.com/1070368
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/heads/master@{#561139}
1 file changed