Deprecate NonThreadSafe in components/sync in favor of SequenceChecker.

components/sync/engine_impl/js_mutation_event_observer.cc

Index: components/sync/engine_impl/js_mutation_event_observer.cc
diff --git a/components/sync/engine_impl/js_mutation_event_observer.cc b/components/sync/engine_impl/js_mutation_event_observer.cc
index 2554b1aafa2fb712a2a37bbad7a21dba15d0eb1a..7b174482100e0aa5b240f09c3f1c650e1d003d44 100644
--- a/components/sync/engine_impl/js_mutation_event_observer.cc
+++ b/components/sync/engine_impl/js_mutation_event_observer.cc
@@ -18,7 +18,7 @@ namespace syncer {
 JsMutationEventObserver::JsMutationEventObserver() : weak_ptr_factory_(this) {}
 
 JsMutationEventObserver::~JsMutationEventObserver() {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 }
 
 base::WeakPtr<JsMutationEventObserver> JsMutationEventObserver::AsWeakPtr() {
@@ -82,7 +82,7 @@ void JsMutationEventObserver::OnChangesComplete(ModelType model_type) {
 void JsMutationEventObserver::OnTransactionWrite(
     const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
     ModelTypeSet models_with_changes) {
-  DCHECK(CalledOnValidThread());
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   if (!event_handler_.IsInitialized()) {
     return;
   }