cipd: Refactor client to make it more readable.

go/src/infra/tools/cipd/clock_test.go

-// Copyright 2014 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 cipd
-
-// No tests in this file, just a mockClock function used from other tests.
-
-import (
-        "time"
-
-        . "github.com/smartystreets/goconvey/convey"
-)
-
-type mockedClocked struct {
-        now time.Time
-}
-
-func (c *mockedClocked) Now() time.Time        { return c.now }
-func (c *mockedClocked) Sleep(d time.Duration) { c.now = c.now.Add(d) }
-
-func mockClock(now time.Time) {
-        prev := clock
-        clock = &mockedClocked{now: now}
-        Reset(func() { clock = prev })
-}