perf: move unrelated types/consts

These are not related to regression detection, so move them from the
middle of the regression functions.

For golang/go#48803.

Change-Id: If9d0d1d7560c54db5da6feb83cdaaffa803ba056
Reviewed-on: https://go-review.googlesource.com/c/build/+/442259
Reviewed-by: David Chase <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Run-TryBot: Michael Pratt <[email protected]>

Author: prattmic

perf/app/dashboard.go

@@ -428,20 +428,6 @@ func groupBenchmarkResults(res *api.QueryTableResult, byRegression bool) ([]*Ben
 	return s, nil
 }
 
-type gzipResponseWriter struct {
-	http.ResponseWriter
-	w *gzip.Writer
-}
-
-func (w *gzipResponseWriter) Write(b []byte) (int, error) {
-	return w.w.Write(b)
-}
-
-const (
-	defaultDays = 30
-	maxDays     = 366
-)
-
 // changeScore returns an indicator of the change and direction.
 // This is a heuristic measure of the lack of overlap between
 // two confidence intervals; minimum lack of overlap (i.e., same
@@ -544,6 +530,20 @@ func worstRegression(b *BenchmarkJSON) regression {
 	return worst
 }
 
+type gzipResponseWriter struct {
+	http.ResponseWriter
+	w *gzip.Writer
+}
+
+func (w *gzipResponseWriter) Write(b []byte) (int, error) {
+	return w.w.Write(b)
+}
+
+const (
+	defaultDays = 30
+	maxDays     = 366
+)
+
 // search handles /dashboard/data.json.
 //
 // TODO(prattmic): Consider caching Influx results in-memory for a few mintures