Move CrostiniRegistryService into namespace crostini

Bug: 813699
Change-Id: I1f185d555dfcc519f46f6f26c8bf6f6aba961b7f
Reviewed-on: https://chromium-review.googlesource.com/981335
Commit-Queue: Renée Wright <rjwright@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#552259}
11 files changed