cmd/benchseries: shorten tests by 2/3, bootstrapping by 1/2, add a skip.

Should be over 90% faster.  Still does useful testing.

Fixes golang/go#53745.

Change-Id: Ide085def6db905d86bdd456a6df41af4d312e536
Reviewed-on: https://go-review.googlesource.com/c/perf/+/459075
Run-TryBot: David Chase <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: dr2chase

cmd/benchseries/main_test.go

@@ -42,6 +42,9 @@ var evenReference = filepath.Join("even", "reference.json")
 // TestReference ensures that each subdirectory generates its
 // reference file.
 func TestReference(t *testing.T) {
+	if testing.Short() {
+		t.Skipf("Skip test, for golang/go#53745")
+	}
 	evens, err := filepath.Glob("testdata/even/*-opt.*")
 	if err != nil {
 		t.Log(err)
@@ -144,7 +147,7 @@ func combineFilesAndJson(t *testing.T, files []string, jsonFile string) []*bench
 	}
 
 	for _, c := range comparisons {
-		c.AddSummaries(0.95, 500) // 500 is faster than 1000.
+		c.AddSummaries(0.95, 250) // 250 is faster than 1000.
 	}
 
 	return comparisons