We want to be able to summarize the behavior of the shell's
performance in a series of "metrics", like the latency between
clicking on the Activities button and seeing a response.
This patch adds the ability to create a script under perf/
in a special format that automates a series of actions in the
shell, writing events to the performance log, then collects
statistics as the log as replayed and turns them into a set
of metrics.
The script is then executed by running as gnome-shell
--perf=<script>.
The 'core' script which is added here will be the primary
performance measurement script that we use for shell performance
regression testing; right now it has a couple of placeholder
metrics.
https://bugzilla.gnome.org/show_bug.cgi?id=618189
