[Sync] TypedUrlSyncableService should filter expired visits from local

components/history/core/browser/typed_url_syncable_service.h

Index: components/history/core/browser/typed_url_syncable_service.h
diff --git a/components/history/core/browser/typed_url_syncable_service.h b/components/history/core/browser/typed_url_syncable_service.h
index 2cbc0c26bdf690fa98bdc3e452ba22dd0636b44e..39f2fd53da9c1fb112527d46e2bd2f980f84ebb6 100644
--- a/components/history/core/browser/typed_url_syncable_service.h
+++ b/components/history/core/browser/typed_url_syncable_service.h
@@ -184,9 +184,12 @@ class TypedUrlSyncableService : public syncer::SyncableService,
   // function compensates for the fact that the history DB has rather poor data
   // integrity (duplicate visits, visit timestamps that don't match the
   // last_visit timestamp, huge data sets that exhaust memory when fetched,
-  // etc) by modifying the passed |url| object and |visits| vector.
-  // Returns false if we could not fetch the visits for the passed URL, and
-  // tracks DB error statistics internally for reporting via UMA.
+  // expired visits that are not deleted by |ExpireHistoryBackend|, etc) by
+  // modifying the passed |url| object and |visits| vector.
+  // Returns false in two cases.
+  // 1. we could not fetch the visits for the passed URL, and tracks DB error
+  // statistics internally for reporting via UMA.
+  // 2. All the visits are expired.
   virtual bool FixupURLAndGetVisits(URLRow* url, VisitVector* visits);
 
   // Given a typed URL in the sync DB, looks for an existing entry in the