[errors] de-specialize Transient in favor of Tags.

common/retry/transient.go

Index: common/retry/transient.go
diff --git a/common/retry/transient.go b/common/retry/transient.go
deleted file mode 100644
index fa641d446df9574cf752afbed012b4e1a08eb44a..0000000000000000000000000000000000000000
--- a/common/retry/transient.go
+++ /dev/null
@@ -1,40 +0,0 @@
-// Copyright 2015 The LUCI Authors. All rights reserved.
-// Use of this source code is governed under the Apache License, Version 2.0
-// that can be found in the LICENSE file.
-
-package retry
-
-import (
-	"time"
-
-	"github.com/luci/luci-go/common/errors"
-	"golang.org/x/net/context"
-)
-
-// transientOnlyIterator is an Iterator implementation that only retries errors
-// if they are transient.
-//
-// (See errors.IsTransient).
-type transientOnlyIterator struct {
-	Iterator // The wrapped Iterator.
-}
-
-func (i *transientOnlyIterator) Next(ctx context.Context, err error) time.Duration {
-	if !errors.IsTransient(err) {
-		return Stop
-	}
-	return i.Iterator.Next(ctx, err)
-}
-
-// TransientOnly returns an Iterator that wraps another Iterator. It will fall
-// through to the wrapped Iterator if a transient error is encountered;
-// otherwise, it will not retry.
-// Returns nil if f is nil.
-func TransientOnly(f Factory) Factory {
-	if f == nil {
-		return nil
-	}
-	return wrap(f, func(it Iterator) Iterator {
-		return &transientOnlyIterator{it}
-	})
-}