[Sync] Refactoring polling to be reliable.

sync/sessions/status_controller.h

 // Copyright 2012 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.
 
 // StatusController handles all counter and status related number crunching and
 // state tracking on behalf of a SyncSession.
 //
 // This object may be accessed from many different threads.  It will be accessed
 // most often from the syncer thread.  However, when update application is in
 // progress it may also be accessed from the worker threads.  This is safe
@@ skipping 38 matching lines @@
   int num_server_conflicts() const;
 
   // Aggregate sum of all conflicting items over all conflict types.
   int TotalNumConflictingItems() const;
 
   // Number of successfully applied updates.
   int num_updates_applied() const;
 
   int num_server_overwrites() const;
 
+  // The time at which we started the first sync cycle in this session.
   base::Time sync_start_time() const {
-    // The time at which we sent the first GetUpdates command for this sync.
     return sync_start_time_;
   }
 
+  // If a poll was performed in this session, the time at which it finished.
+  // Not set if no poll was performed.
+  base::Time poll_finish_time() const {
+    return poll_finish_time_;
+  }
+
   const ModelNeutralState& model_neutral_state() const {
     return model_neutral_;
   }
 
   SyncerError last_get_key_result() const;
 
   // Download counters.
   void increment_num_updates_downloaded_by(int value);
   void increment_num_tombstone_updates_downloaded_by(int value);
   void increment_num_reflected_updates_downloaded_by(int value);
@@ skipping 10 matching lines @@
   void increment_num_successful_commits();
   void increment_num_successful_bookmark_commits();
   void set_num_successful_bookmark_commits(int value);
 
   // Server communication status tracking.
   void set_last_get_key_result(const SyncerError result);
   void set_last_download_updates_result(const SyncerError result);
   void set_commit_result(const SyncerError result);
 
   void UpdateStartTime();
+  void UpdatePollTime();
 
  private:
   ModelNeutralState model_neutral_;
 
+  // Time the last sync cycle began.
   base::Time sync_start_time_;
 
+  // If a poll was performed, the time it finished. Not set if not poll was
+  // performed.
+  base::Time poll_finish_time_;
+
   DISALLOW_COPY_AND_ASSIGN(StatusController);
 };
 
 }  // namespace sessions
 }  // namespace syncer
 
 #endif  // SYNC_SESSIONS_STATUS_CONTROLLER_H_