EXO: Refactored gaming input interface

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

Bug: 896710
Test: Built on ChromeOS
Change-Id: I9202fc459a4f1095d20f83e7d1b64822beca9028
Reviewed-on: https://chromium-review.googlesource.com/c/1323693
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@{#608626}
4 files changed