Add HostCachePersistenceManager for Cronet

components/cronet/host_cache_persistence_manager.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 "components/cronet/host_cache_persistence_manager.h"
+
+#include <memory>
+
+#include "base/memory/ptr_util.h"
+#include "base/values.h"
+#include "components/prefs/pref_service.h"
+
+namespace cronet {
+
+HostCachePersistenceManager::HostCachePersistenceManager(
+    net::HostCache* cache,
+    PrefService* pref_service,
+    std::string pref_name,
+    base::TimeDelta delay)
+    : cache_(cache),
+      pref_service_(pref_service),
+      pref_name_(pref_name),
+      delay_(delay),
+      weak_factory_(this) {
+  DCHECK(cache_);
+  DCHECK(pref_service_);
+
+  // Get the initial value of the pref if it's already initialized.
+  if (pref_service_->HasPrefPath(pref_name_))
+    ReadFromDisk();
+
+  registrar_.Init(pref_service_);
+  registrar_.Add(pref_name_,
+                 base::Bind(&HostCachePersistenceManager::ReadFromDisk,
+                            weak_factory_.GetWeakPtr()));
+  cache_->set_persistence_delegate(this);
+}
+
+HostCachePersistenceManager::~HostCachePersistenceManager() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  timer_.Stop();
+  registrar_.RemoveAll();
+  cache_->set_persistence_delegate(nullptr);
+}
+
+void HostCachePersistenceManager::ReadFromDisk() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  if (writing_pref_)
+    return;
+
+  const base::ListValue* pref_value = pref_service_->GetList(pref_name_);
+  cache_->RestoreFromListValue(*pref_value);
+}
+
+void HostCachePersistenceManager::ScheduleWrite() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  if (timer_.IsRunning())
+    return;
+
+  timer_.Start(FROM_HERE, delay_,
+               base::Bind(&HostCachePersistenceManager::WriteToDisk,
+                          weak_factory_.GetWeakPtr()));
+}
+
+void HostCachePersistenceManager::WriteToDisk() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
+  std::unique_ptr<base::ListValue> value = cache_->GetAsListValue(false);

[pauljensen, 2017/06/23 14:10:31]

I'd prefer if GetAsListValue() took a ListValue* rather than returned a
unique_ptr; it saves a memory allocation and deallocation in cases like this
function.  I'm not sure what the precedent for this is; net::GetNetworkList()
and URLRequest::GetFullHeaders() take pointer to classes that they fill in.

[mgersh, 2017/06/23 16:02:06]

Done.

+  writing_pref_ = true;
+  pref_service_->Set(pref_name_, *value);
+  writing_pref_ = false;
+}
+
+}  // namespace cronet