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* Don't use root window as transient parent in test.
* Don't create WindowState before adding to parent intest.
Instead set the window show type to specify the maximized state.

These are preparations to limit WindowState to specific containers.

Bug: 912191
Test: no functional change. all tests should pass.
Change-Id: Ic4587153395552eb140f06d440c5df7afb5b689a
Reviewed-on: https://chromium-review.googlesource.com/c/1387839
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619701}