[Picture-in-Picture] Add a layout test for detached frame.

This CL adds a test to make sure requesting Picture-in-Picture rejects
when frame is detached.

Bug: 806249
Change-Id: I2f9a029cc03fa8977400f908c87f80ed69674e93
Reviewed-on: https://chromium-review.googlesource.com/1065732
Reviewed-by: Mounir Lamouri <mlamouri@chromium.org>
Commit-Queue: François Beaufort <beaufort.francois@gmail.com>
Cr-Commit-Position: refs/heads/master@{#560605}
3 files changed