Remove libs/clock in favor of luci-go/common/clock.

go/src/infra/libs/clock/clockflag/duration.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 clockflag
-
-import (
-        "errors"
-        "flag"
-        "fmt"
-        "time"
-)
-
-// Duration is a Flag- and JSON-compatible Duration value.
-type Duration time.Duration
-
-var _ flag.Value = (*Duration)(nil)
-
-// Set implements flag.Value.
-func (d *Duration) Set(value string) error {
-        duration, err := time.ParseDuration(value)
-        if err != nil {
-                return err
-        }
-        *d = Duration(duration)
-        return nil
-}
-
-func (d *Duration) String() string {
-        return time.Duration(*d).String()
-}
-
-// Duration returns the Duration value of the flag.
-func (d Duration) Duration() time.Duration {
-        return time.Duration(d)
-}
-
-// IsZero tests if this Duration is the zero value.
-func (d Duration) IsZero() bool {
-        return time.Duration(d) == time.Duration(0)
-}
-
-// UnmarshalJSON implements json.Unmarshaler.
-//
-// Unmarshals a JSON entry into the underlying type. The entry is expected to
-// contain a string corresponding to one of the enum's keys.
-func (d *Duration) UnmarshalJSON(data []byte) error {
-        // Strip off leading and trailing quotes.
-        s := string(data)
-        if len(s) < 2 || s[0] != '"' || s[len(s)-1] != '"' {
-                return errors.New("Duration JSON must be a valid JSON string.")
-        }
-        return d.Set(s[1 : len(s)-1])
-}
-
-// MarshalJSON implements json.Marshaler.
-//
-// Marshals a Duration into a duration string.
-func (d Duration) MarshalJSON() ([]byte, error) {
-        return []byte(fmt.Sprintf(`"%s"`, d.Duration().String())), nil
-}