Add new tests to presubmit, fix errors

perf/go/shortcut/shortcut.go

 // shortcut handles storing and retrieving shortcuts.
 package shortcut
 
 import (
         "encoding/json"
         "fmt"
         "io"
         "io/ioutil"
 
         "skia.googlesource.com/buildbot.git/perf/go/db"
 )
 
 type Shortcut struct {
         Scale int      `json:"scale"`
         Tiles []int    `json:"tiles"`
         Keys  []string `json:"keys"`
         Hash  string   `json:"hash"`
         Issue string   `json:"issue"`
 }
 
 // Insert adds the shortcut content into the database. The id of the shortcut
 // is returned.
 func Insert(r io.Reader) (string, error) {
         b, err := ioutil.ReadAll(r)
         if err != nil {
                 return "", fmt.Errorf("Unable to read shortcut body: %s", err)
         }
         result, err := db.DB.Exec(`INSERT INTO shortcuts (traces) VALUES (?)`, string(b))
         if err != nil {
-                return "", fmt.Errorf("Error while inserting shortcut: err", err)
+                return "", fmt.Errorf("Error while inserting shortcut: %v", err)
         }
         id, err := result.LastInsertId()
         if err != nil {
-                return "", fmt.Errorf("Error retrieving ID of new shortcut:", err)
+                return "", fmt.Errorf("Error retrieving ID of new shortcut: %v", err)
         }
         return fmt.Sprintf("%d", id), nil
 }
 
 // Get retrieves a parsed shortcut for the given id.
 func Get(id string) (*Shortcut, error) {
         var s string
         if err := db.DB.QueryRow(`SELECT traces FROM shortcuts WHERE id =?`, id).Scan(&s); err != nil {
                 return nil, fmt.Errorf("Error retrieving shortcut from db: %s", err)
         }
         ret := &Shortcut{}
         if err := json.Unmarshal([]byte(s), ret); err != nil {
                 return nil, fmt.Errorf("Error decoding shortcut: %s", err)
         }
         return ret, nil
 }