Move retry and lhttp packages from client/internal to common/.

common/lhttp/utils.go

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package lhttp
 
 import (
         "errors"
         "net/url"
         "strings"
 )
 
 // URLToHTTPS ensures the url is https://.
 func URLToHTTPS(s string) (string, error) {
         u, err := url.Parse(s)
         if err != nil {
                 return "", err
         }
         if u.Scheme != "" && u.Scheme != "https" {
                 return "", errors.New("Only https:// scheme is accepted. It can be omitted.")
         }
         if !strings.HasPrefix(s, "https://") {
                 s = "https://" + s
         }
         if _, err = url.Parse(s); err != nil {
                 return "", err
         }
         return s, nil
 }