[Sync] Refactoring polling to be reliable.

sync/internal_api/public/sessions/sync_session_snapshot.h

Index: sync/internal_api/public/sessions/sync_session_snapshot.h
diff --git a/sync/internal_api/public/sessions/sync_session_snapshot.h b/sync/internal_api/public/sessions/sync_session_snapshot.h
index a764de1e7f08cfd3bac6eb6e014139f001b915c7..5b5f075d53badc11cf827ae7b748fff660cc46b9 100644
--- a/sync/internal_api/public/sessions/sync_session_snapshot.h
+++ b/sync/internal_api/public/sessions/sync_session_snapshot.h
@@ -39,6 +39,7 @@ class SYNC_EXPORT SyncSessionSnapshot {
       bool notifications_enabled,
       size_t num_entries,
       base::Time sync_start_time,
+      base::Time poll_finish_time,
       const std::vector<int>& num_entries_by_type,
       const std::vector<int>& num_to_delete_entries_by_type,
       sync_pb::GetUpdatesCallerInfo::GetUpdatesSource legacy_updates_source);
@@ -60,6 +61,7 @@ class SYNC_EXPORT SyncSessionSnapshot {
   bool notifications_enabled() const;
   size_t num_entries() const;
   base::Time sync_start_time() const;
+  base::Time poll_finish_time() const;
   const std::vector<int>& num_entries_by_type() const;
   const std::vector<int>& num_to_delete_entries_by_type() const;
   sync_pb::GetUpdatesCallerInfo::GetUpdatesSource legacy_updates_source() const;
@@ -77,6 +79,7 @@ class SYNC_EXPORT SyncSessionSnapshot {
   bool notifications_enabled_;
   size_t num_entries_;
   base::Time sync_start_time_;
+  base::Time poll_finish_time_;
 
   std::vector<int> num_entries_by_type_;
   std::vector<int> num_to_delete_entries_by_type_;