Tether: Break helper TimerFactory out of BleConnectionManager and HostScanCache.

chromeos/components/tether/timer_factory.cc

+// Copyright 2017 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.
+
+#include "chromeos/components/tether/timer_factory.h"
+
+namespace chromeos {
+
+namespace tether {
+
+TimerFactory::~TimerFactory() {}
+
+std::unique_ptr<base::Timer> TimerFactory::CreateOneShotTimer() {
+  return base::MakeUnique<base::OneShotTimer>();
+}
+
+}  // namespace tether
+
+}  // namespace chromeos