user_activity: Added scripts for collecting the experiment data sets.

BUG=None
TEST=None

Change-Id: I7b00ce4359cb378e45bb673e023c12137d03e9b8
Reviewed-on: https://chrome-internal-review.googlesource.com/287959


Tested-by: Evelina Dumitrescu <evelinad@google.com>
Reviewed-by: George Burgess <gbiv@google.com>
Reviewed-by: Ting-Yuan Huang <laszio@google.com>
Reviewed-by: Evelina Dumitrescu <evelinad@google.com>
Reviewed-on: https://chromium-review.googlesource.com/435909


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