Make TypedUrlSyncableService sequence-affine.

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 313021ded1ae38fec3ec5f04aed2c6233e29a8fe..838e83efc6d77e07b97a08a165974e9d6dcc6886 100644
--- a/components/history/core/browser/typed_url_syncable_service.h
+++ b/components/history/core/browser/typed_url_syncable_service.h
@@ -12,7 +12,7 @@
 
 #include "base/macros.h"
 #include "base/scoped_observer.h"
-#include "base/threading/thread_checker.h"
+#include "base/sequence_checker.h"
 #include "components/history/core/browser/history_backend_observer.h"
 #include "components/history/core/browser/history_types.h"
 #include "components/sync/model/sync_change.h"
@@ -232,7 +232,7 @@ class TypedUrlSyncableService : public syncer::SyncableService,
   int num_db_accesses_;
   int num_db_errors_;
 
-  base::ThreadChecker thread_checker_;
+  base::SequenceChecker sequence_checker_;
 
   ScopedObserver<history::HistoryBackend, history::HistoryBackendObserver>
       history_backend_observer_;