EXO: Refactored stylus_tools interface

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

Bug: 896710
Test: Built on ChromeOS
Change-Id: Ie891710ea8df139f49ae350cd40ec9f083870460
Reviewed-on: https://chromium-review.googlesource.com/c/1324141
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@{#609003}
4 files changed