Replace deprecated base::NonThreadSafe in chrome/browser/extensions in favor of SequenceChecker.

chrome/browser/extensions/warning_badge_service.h

Index: chrome/browser/extensions/warning_badge_service.h
diff --git a/chrome/browser/extensions/warning_badge_service.h b/chrome/browser/extensions/warning_badge_service.h
index f0ea904f8f399c169359e4db7ce9034cfb0de12f..61d39c8b53cafaebacecbfa0052dd4c0075528b5 100644
--- a/chrome/browser/extensions/warning_badge_service.h
+++ b/chrome/browser/extensions/warning_badge_service.h
@@ -7,7 +7,6 @@
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
-#include "base/threading/non_thread_safe.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "extensions/browser/warning_service.h"
 #include "extensions/browser/warning_set.h"
@@ -19,8 +18,7 @@ namespace extensions {
 // A service that is responsible for showing an extension warning badge on the
 // wrench menu.
 class WarningBadgeService : public KeyedService,
-                            public WarningService::Observer,
-                            public base::NonThreadSafe {
+                            public WarningService::Observer {
  public:
   explicit WarningBadgeService(Profile* profile);
   ~WarningBadgeService() override;