Add a SupervisedUserServiceObserver.

chrome/browser/supervised_user/supervised_user_service_observer.h

Index: chrome/browser/supervised_user/supervised_user_service_observer.h
diff --git a/chrome/browser/supervised_user/supervised_user_service_observer.h b/chrome/browser/supervised_user/supervised_user_service_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..27580f6b8e4075b784c126c879c03593ada92824
--- /dev/null
+++ b/chrome/browser/supervised_user/supervised_user_service_observer.h
@@ -0,0 +1,18 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_SERVICE_OBSERVER_H_
+#define CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_SERVICE_OBSERVER_H_
+
+class SupervisedUserServiceObserver {
+ public:
+  // Called whenever the URL filter is updated, e.g. a manual exception or a
+  // content pack is added, or the default fallback behavior is changed.
+  virtual void OnURLFilterChanged() {}
+
+ protected:
+  virtual ~SupervisedUserServiceObserver() {}
+};
+
+#endif  // CHROME_BROWSER_SUPERVISED_USER_SUPERVISED_USER_SERVICE_OBSERVER_H_