Add new tests to presubmit, fix errors

perf/go/activitylog/activitylog.go

 // Package activitylog implements utility for activity logging into database.
 package activitylog
 
 import (
         "fmt"
         "time"
 
         "github.com/golang/glog"
 
         "skia.googlesource.com/buildbot.git/perf/go/db"
         "skia.googlesource.com/buildbot.git/perf/go/types"
 )
 
 // Write writes a new activity record to the db table activitylog.
 // Input is in types.Activity format, but ID and TS are ignored. Instead, always
 // use autoincrement ID and the current timestamp for the new record.
 func Write(r *types.Activity) error {
         glog.Infof("Write activity: %s\n", r)
         if r.UserID == "" || r.Action == "" {
-                return fmt.Errorf("Activity UserID and Action cannot be empty: %s\n", r)
+                return fmt.Errorf("Activity UserID and Action cannot be empty: %v\n", r)
         }
         _, err := db.DB.Exec(
                 "INSERT INTO activitylog (timestamp, userid, action, url) VALUES (?, ?, ?, ?)",
                 time.Now().Unix(), r.UserID, r.Action, r.URL)
         if err != nil {
                 return fmt.Errorf("Failed to write to database: %s", err)
         }
         return nil
 }
 
@@ skipping 20 matching lines @@
                         TS:     timestamp,
                         UserID: userid,
                         Action: action,
                         URL:    url,
                 }
                 ret = append(ret, r)
         }
 
         return ret, nil
 }