Make it clear what last_sync_timestamp actually tracks. Update

chrome/browser/sync/engine/syncer_end_command.cc

Index: chrome/browser/sync/engine/syncer_end_command.cc
diff --git a/chrome/browser/sync/engine/syncer_end_command.cc b/chrome/browser/sync/engine/syncer_end_command.cc
index 3b57618b4744e1bcd45b2e00be4e146b185d65c3..e594542e9079f38e4770d45b497b0029538c6af8 100644
--- a/chrome/browser/sync/engine/syncer_end_command.cc
+++ b/chrome/browser/sync/engine/syncer_end_command.cc
@@ -18,10 +18,9 @@ void SyncerEndCommand::ExecuteImpl(sessions::SyncSession* session) {
   sessions::StatusController* status(session->status_controller());
   status->set_syncing(false);
 
-  if (!session->HasMoreToSync()) {
-    // This might be the first time we've fully completed a sync cycle.
-    DCHECK(status->got_zero_updates());
-
+  // This might be the first time we've fully completed a sync cycle.
+  if (!session->HasMoreToSync() &&
+      status->server_says_nothing_more_to_download()) {
     syncable::ScopedDirLookup dir(session->context()->directory_manager(),
                                   session->context()->account_name());
     if (!dir.good()) {