Move Notification-related Blink API headers into their own directory.

public/platform/WebNotificationPermission.h

Index: public/platform/WebNotificationPermission.h
diff --git a/public/platform/WebNotificationPermission.h b/public/platform/WebNotificationPermission.h
index 424f4b1fa3a3e0067e47feb1d2c04ebb7c79e472..a14479ec4c5f218ffde32852688de264558dba02 100644
--- a/public/platform/WebNotificationPermission.h
+++ b/public/platform/WebNotificationPermission.h
@@ -1,20 +1 @@
-// 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 WebNotificationPermission_h
-#define WebNotificationPermission_h
-
-namespace blink {
-
-enum WebNotificationPermission {
-    WebNotificationPermissionAllowed = 0,
-    WebNotificationPermissionDefault,
-    WebNotificationPermissionDenied,
-
-    WebNotificationPermissionLast = WebNotificationPermissionDenied
-};
-
-} // namespace blink
-
-#endif // WebNotificationPermission_h
+#include "public/platform/modules/notifications/WebNotificationPermission.h"