[Sync] Refactoring polling to be reliable.

sync/sessions/status_controller.h

Index: sync/sessions/status_controller.h
diff --git a/sync/sessions/status_controller.h b/sync/sessions/status_controller.h
index 9844929bcc1f48db51294468702fb082501d9ef3..eea5872338b3d7bf876c13f9ec039a562ff85261 100644
--- a/sync/sessions/status_controller.h
+++ b/sync/sessions/status_controller.h
@@ -56,11 +56,17 @@ class SYNC_EXPORT_PRIVATE StatusController {
 
   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_;
   }
@@ -91,12 +97,18 @@ class SYNC_EXPORT_PRIVATE StatusController {
   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);
 };