event/bench: rename and add benchmarks

Some benchmarks were misnamed.

Change-Id: I092ccc12c2eb3c3505c4c2a0bb8f64fd910a15de
Reviewed-on: https://go-review.googlesource.com/c/exp/+/324292
Trust: Jonathan Amsterdam <jba@google.com>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Ian Cottrell <iancottrell@google.com>
diff --git a/event/bench/event_test.go b/event/bench/event_test.go
index 029fd1c..9043530 100644
--- a/event/bench/event_test.go
+++ b/event/bench/event_test.go
@@ -113,9 +113,17 @@
 }
 
 func BenchmarkTraceEventNoop(b *testing.B) {
+	runBenchmark(b, eventNoop(), eventTrace)
+}
+
+func BenchmarkTraceEventDiscard(b *testing.B) {
 	runBenchmark(b, eventPrint(io.Discard), eventTrace)
 }
 
 func BenchmarkMetricEventNoop(b *testing.B) {
+	runBenchmark(b, eventNoop(), eventMetric)
+}
+
+func BenchmarkMetricEventDiscard(b *testing.B) {
 	runBenchmark(b, eventPrint(io.Discard), eventMetric)
 }