Split out QuicAlarm creation from QuicConnectionHelper to new QuicAlarmFactory.

net/quic/quic_alarm_factory.h

+// Copyright 2013 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.
+
+#ifndef NET_QUIC_QUIC_ALARM_FACTORY_H_
+#define NET_QUIC_QUIC_ALARM_FACTORY_H_
+
+#include "net/quic/quic_alarm.h"
+#include "net/quic/quic_one_block_arena.h"
+
+namespace net {
+
+// QuicConnections currently use around 1KB of polymorphic types which would
+// ordinarily be on the heap. Instead, store them inline in an arena.
+using QuicConnectionArena = QuicOneBlockArena<1024>;
+
+// Creates platform-specific alarms used throughout QUIC.
+class QuicAlarmFactory {
+ public:
+  virtual ~QuicAlarmFactory() {}
+
+  // Creates a new platform-specific alarm which will be configured to notify
+  // |delegate| when the alarm fires. Returns an alarm allocated on the heap.
+  // Caller takes ownership of the new alarm, which will not yet be "set" to
+  // fire.
+  virtual QuicAlarm* CreateAlarm(QuicAlarm::Delegate* delegate) = 0;
+
+  // Creates a new platform-specific alarm which will be configured to notify
+  // |delegate| when the alarm fires. Caller takes ownership of the new alarm,
+  // which will not yet be "set" to fire. If |arena| is null, then the alarm
+  // will be created on the heap. Otherwise, it will be created in |arena|.
+  virtual QuicArenaScopedPtr<QuicAlarm> CreateAlarm(
+      QuicArenaScopedPtr<QuicAlarm::Delegate> delegate,

[Ryan Hamilton, 2016/04/18 22:10:54]

not your responsibility, but we should consider renaming this s/Scoped/Unique/

+      QuicConnectionArena* arena) = 0;
+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_QUIC_ALARM_FACTORY_H_