Remove chrome/browser dep from Chrome OS settings

InstallAttributes and the "Chrome" Schema both have few deps and are
needed in Chrome OS settings code, in code that should be servicified.
See go/ash-settings-split. However, getting a useful instance of
either class currently means depending on chrome/browser to get
browser_process and all of its global services.

This CL makes InstallAttributes and the Chrome Schema singletons that
can also be obtained directly, and so removes one of the dependencies
on chrome/browser from the Chrome OS settings code.

Bug: 446937
Change-Id: If8b1d8e4e9851464278d4b3e25562bc0eea8a41c
Reviewed-on: https://chromium-review.googlesource.com/1141947
Commit-Queue: A Olsen <olsen@chromium.org>
Reviewed-by: Lutz Justen <ljusten@chromium.org>
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Reviewed-by: Bernhard Bauer <bauerb@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Jialiu Lin <jialiul@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582585}
90 files changed