Don't allow splitview for PIPed windows.

BUG=b:109773984
BUG=841886

Change-Id: Ib04cd920450f7e63e779220b24a65956f3bc1e1f
Reviewed-on: https://chromium-review.googlesource.com/1088342
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Stefan Kuhne <skuhne@chromium.org>
Commit-Queue: Eliot Courtney <edcourtney@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566694}
4 files changed