test: Fix flaky PerfettoFtraceIntegrationTest
d04c69d715d4("test: Fix CTS tests on user builds.") changed an ftrace
test event from `sched/sched_process_fork` to `sched/sched_switch`. The
new event is a lot spammier and sometimes causes the RING_BUFFER to wrap
around, overwriting the stats that we're checking.
Use a DISCARD buffer to fix the problem.
Change-Id: I25b6d201a894a8f9a5e6246bcf486b843803708c
Perfetto is a production-grade open-source stack for performance instrumentation and trace analysis. It offers services and libraries and for recording system-level and app-level traces, native + java heap profiling, a library for analyzing traces using SQL and a web-based UI to visualize and explore multi-GB traces.
See https://perfetto.dev/docs or the /docs/ directory for documentation.