EXO: Refactor out CrOS-specific functionality (exo/display)

Prevented ChromeOS-specific funcionality from compiling
for other platforms. To be used for EXO on cast shell.
This CL does not offer any additional functionality.

Bug: 896710
Test: Run exo_unittests on ChromeOS
Change-Id: I72678ae35efce395f932b7d0ade816d61dd6e992
Reviewed-on: https://chromium-review.googlesource.com/c/1327402
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Reviewed-by: Daniele Castagna <dcastagna@chromium.org>
Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612224}
2 files changed