Make SMB file_system_id compound

- Creates a helper class that manages the creation and parsing of
a compound file_system_id.
- Switches to these functions.

Bug: chromium:757625
Change-Id: I611cfdf213da104f1dc63ce7ba442298bd362f41
Reviewed-on: https://chromium-review.googlesource.com/990580
Commit-Queue: Bailey Berro <baileyberro@chromium.org>
Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550635}
7 files changed