Add NetworkTimeTracker::StartTimeFetch() for on-demand time queries

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 <stdint.h>
 #include <memory>
 
 #include "base/feature_list.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.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"
 #include "url/gurl.h"
 
 class PrefRegistrySimple;
 class PrefService;
 
 namespace base {
-class RunLoop;
 class TickClock;
 }  // namespace base
 
 namespace client_update_protocol {
 class Ecdsa;
 }  // namespace client_update_protocol
 
 namespace net {
 class URLFetcher;
 class URLRequestContextGetter;
@@ skipping 62 matching lines @@
   //
   // 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.
   NetworkTimeResult GetNetworkTime(base::Time* network_time,
                                    base::TimeDelta* uncertainty) const;
 
+  // Starts a network time query if network time isn't already available
+  // and if there isn't already a time query in progress. If a new query
+  // is started or if there is one already in progress, |callback| will
+  // run when the query completes.
+  //
+  // Returns true if a time query is started or was already in progress,
+  // and false otherwise. For example, this method may return false if
+  // time queries are disabled or if network time is already available.
+  bool StartTimeFetch(const base::Closure& callback);
+
   // 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);
 
   void SetMaxResponseSizeForTesting(size_t limit);
@@ skipping 35 matching lines @@
   base::TimeDelta backoff_;
   // Timer that runs CheckTime().  All backoff and delay is implemented by
   // changing the delay of this timer, with the result that CheckTime() may
   // assume that if it runs, it is eligible to issue a time query.
   base::RepeatingTimer timer_;
   scoped_refptr<net::URLRequestContextGetter> getter_;
   std::unique_ptr<net::URLFetcher> time_fetcher_;
   base::TimeTicks fetch_started_;
   std::unique_ptr<client_update_protocol::Ecdsa> query_signer_;
 
-  // Run by WaitForFetchForTesting() and quit by OnURLFetchComplete().
-  base::RunLoop* run_loop_for_testing_ = nullptr;
-
   // The |Clock| and |TickClock| are used to sanity-check one another, allowing
   // the NetworkTimeTracker to notice e.g. suspend/resume events and clock
   // resets.
   std::unique_ptr<base::Clock> clock_;
   std::unique_ptr<base::TickClock> tick_clock_;
 
   PrefService* pref_service_;
 
   // Network time based on last call to UpdateNetworkTime().
   mutable base::Time network_time_at_last_measurement_;
 
   // The estimated local times that correspond with |network_time_|. Assumes
   // the actual network time measurement was performed midway through the
   // latency time.  See UpdateNetworkTime(...) implementation for details.  The
   // tick clock is the one actually used to return values to callers, but both
   // clocks must agree to within some tolerance.
   base::Time time_at_last_measurement_;
   base::TimeTicks ticks_at_last_measurement_;
 
   // Uncertainty of |network_time_| based on added inaccuracies/resolution.  See
   // UpdateNetworkTime(...) implementation for details.
   base::TimeDelta network_time_uncertainty_;
 
   // True if any time query has completed (but not necessarily succeeded) in
   // this NetworkTimeTracker's lifetime.
   bool time_query_completed_;
 
+  // Callbacks to run when the in-progress time fetch completes.
+  std::vector<base::Closure> fetch_completion_callbacks_;
+
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker);
 };
 
 }  // namespace network_time
 
 #endif  // COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_