Add Network Quality Estimator (NQE) pref manager

net/nqe/network_qualities_prefs_manager.h

+// Copyright 2016 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_NQE_NETWORK_QUALITIES_PREFS_MANAGER_H_
+#define NET_NQE_NETWORK_QUALITIES_PREFS_MANAGER_H_
+
+#include <memory>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "net/base/net_export.h"
+#include "net/nqe/effective_connection_type.h"
+#include "net/nqe/network_id.h"
+#include "net/nqe/network_quality_store.h"
+
+namespace base {
+class DictionaryValue;
+class SequencedTaskRunner;
+}
+
+namespace net {
+namespace nqe {
+namespace internal {
+class CachedNetworkQuality;
+}
+}
+class NetworkQualityEstimator;
+
+typedef base::Callback<void(
+    const nqe::internal::NetworkID& network_id,
+    const nqe::internal::CachedNetworkQuality& cached_network_quality)>
+    OnChangeInCachedNetworkQualityCallback;
+
+// Using the provided PrefDelegate, NetworkQualitiesPrefsManager creates and
+// updates network quality prefs. Instances of this class must be constructed on

[bengr, 2016/09/22 23:35:46]

network quality prefs -> network quality information that is stored in prefs

[tbansal1, 2016/09/23 17:10:33]

Done.

+// the pref thread, and should later be moved to network thread by calling

[bengr, 2016/09/22 23:35:46]

What is the "pref thread?"

to -> to the

[tbansal1, 2016/09/23 17:10:32]

Thread that is used to access the prefs
(https://cs.chromium.org/search/?q=f:http_server_properties+pref.*thread&sq=pa...).
I did not say "UI" because on cronet, these are accessed on the network task
runner.
Done.

+// InitializeOnNetworkThread.
+//
+// This class interacts with both the pref thread and the network thread, and
+// propagates network quality pref changes from network thread to the provided

[bengr, 2016/09/22 23:35:46]

from -> from the

[tbansal1, 2016/09/23 17:10:32]

Done.

+// pref delegate on the pref thread.
+//
+// ShutdownOnPrefThread must be called from pref thread before destruction.

[bengr, 2016/09/22 23:35:46]

from -> from the

[tbansal1, 2016/09/23 17:10:32]

Done.

+class NET_EXPORT NetworkQualitiesPrefsManager
+    : public nqe::internal::NetworkQualityStore::NetworkQualitiesCacheObserver {
+ public:
+  // Provides an interface that must be implemented by the embedder.
+  class NET_EXPORT PrefDelegate {
+   public:
+    // Sets the persistent pref to the given value.
+    virtual void SetDictionaryValue(const base::DictionaryValue& value) = 0;
+  };
+
+  // Create an instance of the NetworkQualitiesPrefsManager. Ownership of

[bengr, 2016/09/22 23:35:46]

Create -> Creates

[tbansal1, 2016/09/23 17:10:33]

Done.

+  // |pref_delegate| is taken by this class. Must be constructed on the Pref

[bengr, 2016/09/22 23:35:46]

is Pref capitalized? Here and elsewhere.

[tbansal1, 2016/09/23 17:10:32]

Not sure, made it lower case.

+  // thread, and then moved to network thread.
+  explicit NetworkQualitiesPrefsManager(
+      std::unique_ptr<PrefDelegate> pref_delegate);
+  ~NetworkQualitiesPrefsManager() override;
+
+  // Initialize on Network thread.

[bengr, 2016/09/22 23:35:46]

on -> on the

[tbansal1, 2016/09/23 17:10:32]

Done.

+  void InitializeOnNetworkThread(
+      NetworkQualityEstimator* network_quality_estimator);
+
+  // Prepare for shutdown. Must be called on the Pref thread before destruction.
+  void ShutdownOnPrefThread();
+
+ private:
+  // -----------
+  // Pref thread
+  // -----------

[bengr, 2016/09/22 23:35:47]

I would change this comment to simply be:

// Pref thread methods:

Do this to "Network thread" and "Common" as well.

[tbansal1, 2016/09/23 17:10:33]

Done.

+
+  // Called on pref thread when there is a change in the cached network quality.
+  void OnChangeInCachedNetworkQualityOnPrefThread(
+      const nqe::internal::NetworkID& network_id,
+      const nqe::internal::CachedNetworkQuality& cached_network_quality);
+
+  // Responsible for writing the persistent prefs to the disk.
+  std::unique_ptr<PrefDelegate> pref_delegate_;
+
+  scoped_refptr<base::SequencedTaskRunner> pref_task_runner_;
+
+  // Should be accessed only on the pref thread.
+  base::WeakPtr<NetworkQualitiesPrefsManager> pref_weak_ptr_;
+
+  // --------------
+  // Network thread
+  // --------------
+
+  // nqe::internal::NetworkQualityStore::NetworkQualitiesCacheObserver
+  // implementation:
+  void OnChangeInCachedNetworkQuality(
+      const nqe::internal::NetworkID& network_id,
+      const nqe::internal::CachedNetworkQuality& cached_network_quality)
+      override;
+
+  NetworkQualityEstimator* network_quality_estimator_;
+
+  scoped_refptr<base::SequencedTaskRunner> network_task_runner_;
+
+  // --------------
+  // Common
+  // --------------
+
+  // Used to get |weak_ptr_| to self on the pref thread.
+  base::WeakPtrFactory<NetworkQualitiesPrefsManager> pref_weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(NetworkQualitiesPrefsManager);
+};
+
+}  // namespace net
+
+#endif  // NET_NQE_NETWORK_QUALITIES_PREFS_MANAGER_H_