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

go/src/infra/libs/clock/clockflag/duration.go

Index: go/src/infra/libs/clock/clockflag/duration.go
diff --git a/go/src/infra/libs/clock/clockflag/duration.go b/go/src/infra/libs/clock/clockflag/duration.go
deleted file mode 100644
index bddccb657f181645286d39fc3b3386a466703a1f..0000000000000000000000000000000000000000
--- a/go/src/infra/libs/clock/clockflag/duration.go
+++ /dev/null
@@ -1,61 +0,0 @@
-// 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
-}