When SHELL_PERF_OUTPUT is set, instead of just dumping out the metrics, dump
a more complete report with:
- Event descriptions
- Metric descriptions and value
- Event log
Helper functions shell_perf_log_dump_events() and shell_perf_log_dump_log()
are added to ShellPerfLog to support this. The gnome-shell wrapper is adapted
to deal with the changed report format.
https://bugzilla.gnome.org/show_bug.cgi?id=618189