Implement throttling logic for fetching affiliation information.

components/password_manager/core/browser/affiliation_fetch_throttler.h

+// Copyright 2015 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_PASSWORD_MANAGER_CORE_BROWSER_AFFILIATION_FETCH_THROTTLER_H_
+#define COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_AFFILIATION_FETCH_THROTTLER_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "net/base/network_change_notifier.h"
+
+namespace base {
+class TickClock;
+class SingleThreadTaskRunner;
+}  // namespace base
+
+namespace net {
+class BackoffEntry;
+}  // namespace net
+
+namespace password_manager {
+
+class AffiliationFetchThrottlerDelegate;
+
+// Implements the throttling logic that AffiliationBackend will use when it
+// needs to issue requests over the network to fetch affiliation information.
+//
+// Essentially, the logic consists of exponential backoff in case of network and
+// server errors, plus the additional constraint that no requests will be issued
+// in the first place while there is known to be no network connectivity.
+class AffiliationFetchThrottler
+    : public net::NetworkChangeNotifier::ConnectionTypeObserver {
+ public:
+  // Creates an instance that will use |tick_clock| as its tick source, and will
+  // post to |task_runner| to call the |delegate|'s OnSendNetworkRequest().
+  AffiliationFetchThrottler(
+      AffiliationFetchThrottlerDelegate* delegate,
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner,

[mmenke, 2015/01/16 21:28:35]

const scoped_reftr<...>&, to avoid an extra ref count increment/decrement?

[engedy, 2015/01/19 18:13:11]

Done.

+      scoped_ptr<base::TickClock> tick_clock);
+  ~AffiliationFetchThrottler() override;
+
+  // Signals to the throttling logic that a network request is needed, and that
+  // OnCanSendNetworkRequest() should be called as soon as the request can be
+  // sent. Calls to this method will be ignored while a request is in flight.
+  void SignalNetworkRequestNeeded();
+
+  // Informs the back-off logic that the in-flight network request has been
+  // completed, either with |success| or not.
+  void InformOfNetworkRequestComplete(bool success);
+
+ protected:

[mmenke, 2015/01/16 21:28:35]

I think these can all be private.

[engedy, 2015/01/19 18:13:11]

Done.

+  enum State { IDLE, FETCH_NEEDED, FETCH_IN_FLIGHT };
+
+  // Ensures that OnBackoffDelayExpiredCallback() is scheduled to be called back
+  // once the |exponential_backoff_| delay expires.
+  void EnsureCallbackIsScheduled();
+
+  // Called back when the |exponential_backoff_| delay expires.
+  void OnBackoffDelayExpiredCallback();
+
+  // net::NetworkChangeNotifier::ConnectionTypeObserver:
+  void OnConnectionTypeChanged(
+      net::NetworkChangeNotifier::ConnectionType type) override;
+
+ private:
+  AffiliationFetchThrottlerDelegate* delegate_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  State state_;
+  bool has_network_connectivity_;
+  bool is_fetch_scheduled_;
+  scoped_ptr<base::TickClock> tick_clock_;
+  scoped_ptr<net::BackoffEntry> exponential_backoff_;
+  base::WeakPtrFactory<AffiliationFetchThrottler> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(AffiliationFetchThrottler);
+};
+
+}  // namespace password_manager
+
+#endif  // COMPONENTS_PASSWORD_MANAGER_CORE_BROWSER_AFFILIATION_FETCH_THROTTLER_H_