Test FilesApp QuickView [open] attribute

FileApp QuickView has an [open] attribute, present when it (QuickView)
is open, and removed when it's not open. Verify the attribute appears,
and disappears, for all quick_view.js tests.

No change in behavior, no new tests.

Bug: 891150
Change-Id: If90ae81cd60cd350497dece3896173f432571ccc
Reviewed-on: https://chromium-review.googlesource.com/1256465
Reviewed-by: Luciano Pacheco <lucmult@chromium.org>
Commit-Queue: Noel Gordon <noel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595732}
1 file changed