Replace deprecated base::NonThreadSafe in components/reading_list in favor of SequenceChecker.

components/reading_list/core/reading_list_store.h

Index: components/reading_list/core/reading_list_store.h
diff --git a/components/reading_list/core/reading_list_store.h b/components/reading_list/core/reading_list_store.h
index 9f6eef8abfd371abaf4e11458122ef271908d44b..eca26da87d289ff8bba1cd104b02186c94f02da8 100644
--- a/components/reading_list/core/reading_list_store.h
+++ b/components/reading_list/core/reading_list_store.h
@@ -8,7 +8,7 @@
 #include <memory>
 #include <string>
 
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "components/reading_list/core/reading_list_model_storage.h"
 #include "components/reading_list/core/reading_list_store_delegate.h"
 #include "components/sync/model/model_error.h"
@@ -21,8 +21,7 @@ class MutableDataBatch;
 class ReadingListModel;
 
 // A ReadingListModelStorage storing and syncing data in protobufs.
-class ReadingListStore : public ReadingListModelStorage,
-                         public base::NonThreadSafe {
+class ReadingListStore : public ReadingListModelStorage {
   using StoreFactoryFunction = base::Callback<void(
       const syncer::ModelTypeStore::InitCallback& callback)>;
 
@@ -168,6 +167,8 @@ class ReadingListStore : public ReadingListModelStorage,
 
   base::Clock* clock_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(ReadingListStore);
 };