GitLab

In preparation for RootWindowController to own a SplitViewController,
the present CL arranges for the objects to be created at about the same
time, and destroyed at about the same time.

Bug: 970013
Change-Id: I0bcb60c76055124521dd3a33c4a06a299e9ccf0c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1811639
Commit-Queue: Avery Musbach <amusbach@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#698631}