GitLab

Move xdg_shell interface  out of server.cc
This CL only moves code around.

Bug: 896710
Test: Built on ChromeOS
Change-Id: Idb117f086ffa995661291772b122b261aa869794
Reviewed-on: https://chromium-review.googlesource.com/c/1323901
Commit-Queue: Shawn Gallea <sagallea@google.com>
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608666}