Add a Mac UMA for the filesystem where Chrome lives.

BUG=914393

Change-Id: Ia9813b162121de8c3763ccafc6525a628370f5ac
Reviewed-on: https://chromium-review.googlesource.com/c/1371936
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615934}
3 files changed