Replace deprecated base::NonThreadSafe in content in favor of SequenceChecker.

content/public/browser/notification_registrar.h

Index: content/public/browser/notification_registrar.h
diff --git a/content/public/browser/notification_registrar.h b/content/public/browser/notification_registrar.h
index 9097f8fbe2e7e068fbf21b744978137de346c346..8f785420492d8605794a52e4d65ac4eef0ea27bb 100644
--- a/content/public/browser/notification_registrar.h
+++ b/content/public/browser/notification_registrar.h
@@ -8,7 +8,7 @@
 #include <vector>
 
 #include "base/macros.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/sequence_checker.h"
 #include "content/common/content_export.h"
 
 namespace content {
@@ -23,8 +23,7 @@ class NotificationSource;
 // class and use it to register your notifications instead of going through the
 // notification service directly. It will automatically unregister them for
 // you.
-class CONTENT_EXPORT NotificationRegistrar :
-    NON_EXPORTED_BASE(public base::NonThreadSafe) {
+class CONTENT_EXPORT NotificationRegistrar {
  public:
   // This class must not be derived from (we don't have a virtual destructor so
   // it won't work). Instead, use it as a member in your class.
@@ -63,6 +62,8 @@ class CONTENT_EXPORT NotificationRegistrar :
   // Lists all notifications we're currently registered for.
   RecordVector registered_;
 
+  SEQUENCE_CHECKER(sequence_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(NotificationRegistrar);
 };