The plugin process is good for running a VM that depends substantially
on devices that aren't implemented inside of crosvm.
TEST=cargo build --features plugin; ./build_test
BUG=chromium:800626
Change-Id: I7b4f656563742cd0bedc837205dd1240d497941d
Reviewed-on: https://chromium-review.googlesource.com/869357
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Zach Reizner <zachr@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
