ChromeOS: Implement periodic timezone refresh on geolocation data.

chromeos/timezone/timezone_resolver.h

+// Copyright 2014 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 CHROMEOS_TIMEZONE_TIMEZONE_RESOLVER_H_
+#define CHROMEOS_TIMEZONE_TIMEZONE_RESOLVER_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/threading/thread_checker.h"
+#include "chromeos/chromeos_export.h"
+#include "url/gurl.h"
+
+class PrefRegistrySimple;
+class PrefService;
+
+namespace net {
+class URLRequestContextGetter;
+}
+
+namespace chromeos {
+
+struct TimeZoneResponseData;
+
+// This class implements periodic timezone synchronization.
+class CHROMEOS_EXPORT TimeZoneResolver {
+ public:
+  class TimeZoneResolverImpl;
+
+  // This callback will be called when new timezone arrives.
+  typedef base::Callback<void(const TimeZoneResponseData*)>
+      ApplyTimeZoneCallback;
+
+  // chromeos::DelayNetworkCall cannot be used directly due to link
+  // restrictions.
+  typedef base::Callback<void(const base::Closure&)> DelayNetworkCallClosure;
+
+  // This is a LocalState preference to store base::Time value of the last
+  // request.
+  // It is used to limit request rate on browser restart.
+  static const char kLastTimeZoneRefreshTime[];
+
+  TimeZoneResolver(net::URLRequestContextGetter* context,
+                   const GURL& url,
+                   const ApplyTimeZoneCallback& apply_timezone,
+                   const DelayNetworkCallClosure& delay_network_call,
+                   PrefService* local_state);
+  ~TimeZoneResolver();
+
+  // Starts periodic timezone refresh.
+  void Start();
+
+  // Cancels current request and stops periodic timezone refresh.
+  void Stop();
+
+  // Register prefs to LocalState.
+  static void RegisterPrefs(PrefRegistrySimple* registry);
+
+  // Expose internal fuctions for testing.
+  static int MaxRequestsCountForIntervalForTesting(
+      const double interval_seconds);
+  static int IntervalForNextRequestForTesting(const int requests);
+
+ private:
+  net::URLRequestContextGetter* const context_;
+  const GURL url_;
+
+  const ApplyTimeZoneCallback apply_timezone_;
+  const DelayNetworkCallClosure delay_network_call_;
+  PrefService* local_state_;
+
+  scoped_ptr<TimeZoneResolverImpl> implementation_;
+
+  base::ThreadChecker thread_checker_;
+
+  DISALLOW_COPY_AND_ASSIGN(TimeZoneResolver);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_TIMEZONE_TIMEZONE_RESOLVER_H_