network_time_tracker: add temporary time protocol.

components/network_time/network_time_tracker.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 COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
 #define COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
 
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/clock.h"
 #include "base/time/time.h"
+#include "base/timer/timer.h"
+#include "net/url_request/url_fetcher_delegate.h"
 
 class PrefRegistrySimple;
 class PrefService;
 
 namespace base {
 class TickClock;
 }
 
+namespace client_update_protocol {
+class Ecdsa;
+}
+
+namespace net {
+class URLFetcher;
+class URLRequestContextGetter;
+}
+
 namespace network_time {
 
 // Clock resolution is platform dependent.
 #if defined(OS_WIN)
 const int64_t kTicksResolutionMs = base::Time::kMinLowResolutionThresholdMs;
 #else
 const int64_t kTicksResolutionMs = 1;  // Assume 1ms for non-windows platforms.
 #endif
 
+struct NetworkTimeTrackerPeer;
+
 // A class that receives network time updates and can provide the network time
 // for a corresponding local time. This class is not thread safe.
-class NetworkTimeTracker {
+class NetworkTimeTracker : public net::URLFetcherDelegate {
  public:
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
+  // Constructor.  Arguments may be stubbed out for tests.  |getter|, if not
+  // null, will cause automatic queries to a time server.  Otherwise, time is
+  // available only if |UpdateNetworkTime| is called.
   NetworkTimeTracker(scoped_ptr<base::Clock> clock,
                      scoped_ptr<base::TickClock> tick_clock,
-                     PrefService* pref_service);
-  ~NetworkTimeTracker();
+                     PrefService* pref_service,
+                     net::URLRequestContextGetter* getter = nullptr);
+  ~NetworkTimeTracker() override;
 
   // Sets |network_time| to an estimate of the true time.  Returns true if time
   // is available, and false otherwise.  If |uncertainty| is non-NULL, it will
   // be set to an estimate of the error range.
   //
   // Network time may be available on startup if deserialized from a pref.
   // Failing that, a call to |UpdateNetworkTime| is required to make time
   // available to callers of |GetNetworkTime|.  Subsequently, network time may
   // become unavailable if |NetworkTimeTracker| has reason to believe it is no
   // longer accurate.  Consumers should even be prepared to handle the case
   // where calls to |GetNetworkTime| never once succeeds.
   bool GetNetworkTime(base::Time* network_time,
                       base::TimeDelta* uncertainty) const;
 
   // Calculates corresponding time ticks according to the given parameters.
   // The provided |network_time| is precise at the given |resolution| and
   // represent the time between now and up to |latency| + (now - |post_time|)
   // ago.
   void UpdateNetworkTime(base::Time network_time,
                          base::TimeDelta resolution,
                          base::TimeDelta latency,
                          base::TimeTicks post_time);
 
  private:
+  friend struct NetworkTimeTrackerPeer;
+
+  // Sends a query to the secure time service.  Upon response, execution resumes
+  // in |OnURLFetchComplete|.
+  void QueryTimeService();
+
+  // Called to process responses from the secure time service.

[estark, 2016/03/28 17:35:10]

Preface this section with

// net::URLFetcherDelegate:

[mab, 2016/03/28 19:56:26]

Done.

+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  // State variables for internally-managed secure time service queries.
+  base::RepeatingTimer query_timer_;
+  net::URLRequestContextGetter* getter_;
+  scoped_ptr<net::URLFetcher> time_fetcher_;
+  base::TimeTicks fetch_started_;
+  scoped_ptr<client_update_protocol::Ecdsa> query_signer_;
+
   // The |Clock| and |TickClock| are used to sanity-check one another, allowing
   // the NetworkTimeTracker to notice e.g. suspend/resume events and clock
   // resets.
   scoped_ptr<base::Clock> clock_;
   scoped_ptr<base::TickClock> tick_clock_;
 
   PrefService* pref_service_;
 
   // Network time based on last call to UpdateNetworkTime().
   mutable base::Time network_time_at_last_measurement_;
@@ skipping 13 matching lines @@
   base::ThreadChecker thread_checker_;
 
   bool received_network_time_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker);
 };
 
 }  // namespace network_time
 
 #endif  // COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_