Add HostCachePersistenceManager for Cronet

components/cronet/host_cache_persistence_manager.h

Index: components/cronet/host_cache_persistence_manager.h
diff --git a/components/cronet/host_cache_persistence_manager.h b/components/cronet/host_cache_persistence_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..76a64894c49d4155ca8ecf2d6795c586062aefc6
--- /dev/null
+++ b/components/cronet/host_cache_persistence_manager.h
@@ -0,0 +1,68 @@
+// 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.
+
+#ifndef COMPONENTS_CRONET_HOST_CACHE_PERSISTENCE_MANAGER_H_
+#define COMPONENTS_CRONET_HOST_CACHE_PERSISTENCE_MANAGER_H_
+
+#include <memory>
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/sequence_checker.h"
+#include "base/time/time.h"
+#include "net/dns/host_cache.h"
+
+class PrefChangeRegistrar;
+class PrefService;
+
+namespace base {
+class OneShotTimer;
+}
+
+namespace cronet {
+// Handles the interaction between HostCache and prefs for persistence.
+// On write, starts a timer, or ignores if the timer is already running. When
+// that timer expires, writes the current state of the HostCache to prefs.
+//
+// Can be used with synchronous or asynchronous prefs loading. Not appropriate
+// for use outside of Cronet because its network and prefs operations run on
+// the same sequence. Must be created after and destroyed before the HostCache
+// and PrefService.
+class HostCachePersistenceManager : public net::HostCache::PersistenceDelegate {
+ public:
+  HostCachePersistenceManager(net::HostCache* cache,

[pauljensen, 2017/06/22 19:03:51]

Can you add a comment here explaining the arguments?

[mgersh, 2017/06/22 21:27:32]

Done.

+                              PrefService* pref_service,
+                              std::string pref_name,
+                              base::TimeDelta delay);
+  ~HostCachePersistenceManager();
+
+  // HostCache::PersistenceDelegate implementation
+  void ScheduleWrite() override;
+
+ private:
+  // Gets the serialized HostCache and writes it to prefs.
+  void DoWrite();
+  // On initial prefs read, passes the serialized entries to the HostCache.
+  void OnRead();
+
+  net::HostCache* cache_;

[pauljensen, 2017/06/22 19:03:50]

add const, then we can remove all but the constructor's DCHECK(cache_)

[mgersh, 2017/06/22 21:27:32]

Done.

+
+  std::unique_ptr<PrefChangeRegistrar> registrar_;

[pauljensen, 2017/06/22 19:03:51]

remove the unique_ptr, so just PrefChangeRegistrar

[mgersh, 2017/06/22 21:27:32]

Done.

+  PrefService* pref_service_;

[pauljensen, 2017/06/22 19:03:51]

add const, then we can remove all but the constructor's DCHECK(cache_)

[mgersh, 2017/06/22 21:27:32]

Done.

+  const std::string pref_name_;
+  bool writing_pref_;
+
+  base::TimeDelta delay_;

[pauljensen, 2017/06/22 19:03:50]

const

[mgersh, 2017/06/22 21:27:32]

Done.

+  std::unique_ptr<base::OneShotTimer> timer_;

[pauljensen, 2017/06/22 19:03:50]

remove the unique_ptr, so just base::OneShotTimer

[mgersh, 2017/06/22 21:27:32]

Done.

+
+  SEQUENCE_CHECKER(sequence_checker_);
+  base::WeakPtrFactory<HostCachePersistenceManager> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostCachePersistenceManager);
+};
+
+}  // namespace cronet
+
+#endif  // COMPONENTS_CRONET_HOST_CACHE_PERSISTENCE_MANAGER_H_