test-results: Get handler cleanup

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

 package frontend
 
 import (
         "bytes"
         "encoding/json"
         "io"
         "net/http"
         "regexp"
         "sort"
         "strings"
@@ skipping 88 matching lines @@
         case nil:
                 res = item.Value()
 
         default:
                 logging.WithError(err).Errorf(c, "builders: GetBuilders")
                 http.Error(w, err.Error(), http.StatusInternalServerError)
                 return
         }
 
         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)
 
         if err != nil {
                 logging.Fields{
                         logging.ErrorKey: err,
                         "n":              n,
                 }.Errorf(c, "builders: GetBuilders: failed to write response")
         }
@@ skipping 261 matching lines @@
         // data, we just keep everything before the first space.
         if i := strings.Index(name, " "); i != -1 {
                 name = name[:i]
         }
 
         if withPatch {
                 name += " (with patch)"
         }
         return name
 }