Reland "Separate out source sets for src/chromeos subdirs"

Bug: 446937
Change-Id: I499911436c77a524a93ffd2a42ced50f85d648b4
Reviewed-on: https://chromium-review.googlesource.com/c/1273525
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: A Olsen <olsen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#598446}
5 files changed