test-results: Get handler cleanup

go/src/infra/appengine/test-results/frontend/builders.go

Index: go/src/infra/appengine/test-results/frontend/builders.go
diff --git a/go/src/infra/appengine/test-results/frontend/builders.go b/go/src/infra/appengine/test-results/frontend/builders.go
index d85e04fa573229c0828d28e60cf9353abd11eee8..40f1849c92bb70ed14f4b6d88be677902adfe420 100644
--- a/go/src/infra/appengine/test-results/frontend/builders.go
+++ b/go/src/infra/appengine/test-results/frontend/builders.go
@@ -106,8 +106,8 @@ func GetBuilders(ctx *router.Context) {
 	}
 
 	var out io.Reader = bytes.NewReader(res)
-	if callback := r.FormValue("callback"); callback != "" {
-		out = wrapCallback(out, callback)
+	if c := r.FormValue("callback"); callbackNameRx.MatchString(c) {
+		out = wrapCallback(out, c)
 	}
 
 	n, err := io.Copy(w, out)