Add context-aware "time" library wrapper.

go/src/infra/libs/clock/timer.go

Index: go/src/infra/libs/clock/timer.go
diff --git a/go/src/infra/libs/clock/timer.go b/go/src/infra/libs/clock/timer.go
new file mode 100644
index 0000000000000000000000000000000000000000..f9885c34743165b8c6ae5f88d5ff24462bc5b931
--- /dev/null
+++ b/go/src/infra/libs/clock/timer.go
@@ -0,0 +1,16 @@
+// 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 clock
+
+import (
+	"time"
+)
+
+// Timer is a wrapper around the time.Timer structure.
+type Timer interface {
+	GetC() <-chan time.Time     // Returns the underlying timer's channel, or nil if not configured.
+	Reset(d time.Duration) bool // See time.Timer.
+	Stop() bool                 // See time.Timer.
+}