network_time_tracker: add temporary time protocol.

components/network_time/network_time_tracker.h

Index: components/network_time/network_time_tracker.h
diff --git a/components/network_time/network_time_tracker.h b/components/network_time/network_time_tracker.h
index dc7524a58302b2748c33941bc40938a73f792392..cc1d7d807bbb225c6783179c989b3f445cf580ce 100644
--- a/components/network_time/network_time_tracker.h
+++ b/components/network_time/network_time_tracker.h
@@ -10,6 +10,8 @@
 #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;
@@ -18,6 +20,15 @@ namespace base {
 class TickClock;
 }
 
+namespace client_update_protocol {
+class Ecdsa;
+}
+
+namespace net {
+class URLFetcher;
+class URLRequestContextGetter;
+}
+
 namespace network_time {
 
 // Clock resolution is platform dependent.
@@ -27,16 +38,22 @@ const int64_t kTicksResolutionMs = base::Time::kMinLowResolutionThresholdMs;
 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
@@ -61,6 +78,22 @@ class NetworkTimeTracker {
                          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.