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

components/policy/core/common/schema_registry.h

Index: components/policy/core/common/schema_registry.h
diff --git a/components/policy/core/common/schema_registry.h b/components/policy/core/common/schema_registry.h
index ba422d2d2050fef9637023da9aea0743f708883e..fbe9d4d4acb2e79edf03221bc46b06580a68d368 100644
--- a/components/policy/core/common/schema_registry.h
+++ b/components/policy/core/common/schema_registry.h
@@ -11,7 +11,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "components/policy/core/common/policy_namespace.h"
 #include "components/policy/core/common/schema.h"
 #include "components/policy/core/common/schema_map.h"
@@ -25,7 +25,7 @@ class SchemaMap;
 // observers to get notified whenever it is updated.
 // This object is not thread safe and must be used from the owner's thread,
 // usually UI.
-class POLICY_EXPORT SchemaRegistry : public base::NonThreadSafe {
+class POLICY_EXPORT SchemaRegistry {
  public:
   class POLICY_EXPORT Observer {
    public:
@@ -98,6 +98,8 @@ class POLICY_EXPORT SchemaRegistry : public base::NonThreadSafe {
   base::ObserverList<InternalObserver, true> internal_observers_;
   bool domains_ready_[POLICY_DOMAIN_SIZE];
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(SchemaRegistry);
 };