Add CryptAuthKeyRegistry class

The CryptAuthKeyRegistry stores key bundles that are enrolled with
CryptAuth. This storage is persisted as a pref, and retrieved on
construction.

Bug: 899080
Change-Id: Ifad5bb2d4ce38de43420061fb375f4fe43416ed4
Reviewed-on: https://chromium-review.googlesource.com/c/1407257
Commit-Queue: Josh Nohle <nohle@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#625238}
8 files changed