Cleanup: Fix content header include guards.

content/public/test/mock_notification_observer.h

Index: content/public/test/mock_notification_observer.h
diff --git a/content/public/test/mock_notification_observer.h b/content/public/test/mock_notification_observer.h
index 1c324849c27d326faf6965c4ced43ad44012ff09..c81efe5aafa341e65366b59d6376b3245f9751a3 100644
--- a/content/public/test/mock_notification_observer.h
+++ b/content/public/test/mock_notification_observer.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CONTENT_PUBLIC_TEST_MOCK_NOTIFICATION_OBSERVER_MOCK_H_
-#define CONTENT_PUBLIC_TEST_MOCK_NOTIFICATION_OBSERVER_MOCK_H_
+#ifndef CONTENT_PUBLIC_TEST_MOCK_NOTIFICATION_OBSERVER_H_
+#define CONTENT_PUBLIC_TEST_MOCK_NOTIFICATION_OBSERVER_H_
 
 #include "content/public/browser/notification_observer.h"
 #include "testing/gmock/include/gmock/gmock.h"
@@ -25,4 +25,4 @@ class MockNotificationObserver : public NotificationObserver {
 
 }  // namespace content
 
-#endif  // CONTENT_PUBLIC_TEST_MOCK_NOTIFICATION_OBSERVER_MOCK_H_
+#endif  // CONTENT_PUBLIC_TEST_MOCK_NOTIFICATION_OBSERVER_H_