Deprecate NonThreadSafe in components/sync in favor of SequenceChecker.

components/sync/model_impl/model_type_store_impl.h

Index: components/sync/model_impl/model_type_store_impl.h
diff --git a/components/sync/model_impl/model_type_store_impl.h b/components/sync/model_impl/model_type_store_impl.h
index 3870329912a8bbbd38f5ff679fa0fb758af3a481..3889becc0aacd893b46763ebe3e26f8508b4b13f 100644
--- a/components/sync/model_impl/model_type_store_impl.h
+++ b/components/sync/model_impl/model_type_store_impl.h
@@ -10,8 +10,8 @@
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/sequence_checker.h"
 #include "base/sequenced_task_runner.h"
-#include "base/threading/non_thread_safe.h"
 #include "components/sync/base/model_type.h"
 #include "components/sync/model/model_type_store.h"
 
@@ -26,7 +26,7 @@ class ModelTypeStoreBackend;
 // ModelTypeStoreImpl handles details of store initialization, threading and
 // leveldb key formatting. Actual leveldb IO calls are performed by
 // ModelTypeStoreBackend.
-class ModelTypeStoreImpl : public ModelTypeStore, public base::NonThreadSafe {
+class ModelTypeStoreImpl : public ModelTypeStore {
  public:
   ~ModelTypeStoreImpl() override;
 
@@ -122,6 +122,8 @@ class ModelTypeStoreImpl : public ModelTypeStore, public base::NonThreadSafe {
   // Key for this type's global metadata record.
   const std::string global_metadata_key_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   base::WeakPtrFactory<ModelTypeStoreImpl> weak_ptr_factory_;
 };