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 7f2eb8792031d2cf56c13c17dda1b49909a0e000..852831b45d683bd89bd569295bd3f56d5c57daf4 100644
--- a/components/network_time/network_time_tracker.h
+++ b/components/network_time/network_time_tracker.h
@@ -7,17 +7,29 @@
 
 #include <memory>
 
+#include "base/gtest_prod_util.h"
 #include "base/macros.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 base
+
+namespace client_update_protocol {
+class Ecdsa;
+}  // namespace client_udpate_protocol
+
+namespace net {
+class URLFetcher;
+class URLRequestContextGetter;
+}  // namespace net
 
 namespace network_time {
 
@@ -30,14 +42,18 @@ const int64_t kTicksResolutionMs = 1;  // Assume 1ms for non-windows platforms.
 
 // 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(std::unique_ptr<base::Clock> clock,
                      std::unique_ptr<base::TickClock> tick_clock,
-                     PrefService* pref_service);
-  ~NetworkTimeTracker();
+                     PrefService* pref_service,
+                     net::URLRequestContextGetter* getter = nullptr);

[Ryan Sleevi, 2016/04/28 01:08:34]

URLRequestContextGetter is designed to be ref-counted and can be safely held on
to by clients, to ensure that they can actually get from the getter (if the
underlying URLRequestContext goes away, it behaves safely)

I believe you should be passing this as a
scoped_refptr<net::URLRequestContextGetter>, and storing as such.

[mab, 2016/04/28 02:29:04]

Good catch, thank you.  Done.

[mmenke, 2016/04/28 15:17:08]

Only certainly URLRequestContextGetters are safely shut down - it requires
coordination between the URLRequestContextGetter and the URLREquestContext's
owner for that to work.  Currently, only the Profile's URLRequestContextGetters
shutdown properly.  The system and proxy URLRequestContexts use another magic
path to shut down safely, so I suppose those should be fine, too.  Others can
only be used safely if you're destroyed before the URLRequestContext itself is.

Regardless, this code should definitely be hanging on to a reference, rather
than a raw pointer.

[mab, 2016/04/29 19:42:07]

Done.

+  ~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
@@ -62,6 +78,27 @@ class NetworkTimeTracker {
                          base::TimeTicks post_time);
 
  private:
+  friend class NetworkTimeTrackerTest;
+  FRIEND_TEST_ALL_PREFIXES(NetworkTimeTrackerTest, UpdateFromNetwork);
+  FRIEND_TEST_ALL_PREFIXES(NetworkTimeTrackerTest, NoNetworkQueryWhileSynced);
+  FRIEND_TEST_ALL_PREFIXES(NetworkTimeTrackerTest,
+                           UpdateFromNetworkBadSignature);
+
+  // If synchronization has been lost, sends a query to the secure time service.
+  // Upon response, execution resumes in |OnURLFetchComplete|.
+  void QueryTimeService();
+
+  // net::URLFetcherDelegate:
+  // Called to process responses from the secure time service.
+  void OnURLFetchComplete(const net::URLFetcher* source) override;
+
+  // State variables for internally-managed secure time service queries.
+  base::RepeatingTimer query_timer_;
+  net::URLRequestContextGetter* getter_;
+  std::unique_ptr<net::URLFetcher> time_fetcher_;
+  base::TimeTicks fetch_started_;
+  std::unique_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.