user_activity_benchmarks: Added file with function groups that

represent ChromeOS components.

A function belongs to a group that is defined by a given file path
if it is declared in a file that shares that path.

BUG=None
TEST=None

Change-Id: Ic5b9fd8871d0fc53f10590b63d9277ec2fce6dd8
Reviewed-on: https://chrome-internal-review.googlesource.com/282196


Tested-by: Evelina Dumitrescu <evelinad@google.com>
Reviewed-by: George Burgess <gbiv@google.com>
Reviewed-by: Luis Lozano <llozano@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/435455


Commit-Ready: Luis Lozano <llozano@chromium.org>
Tested-by: Luis Lozano <llozano@chromium.org>