Use UNUSED_PARAM instead of the void casting to suppress unused parameter warnings.

Use UNUSED_PARAM instead of the void casting to suppress unused parameter warnings.
https://bugs.webkit.org/show_bug.cgi?id=143750

Patch by Sungmann Cho <sungmann.cho@navercorp.com> on 2015-04-16
Reviewed by Darin Adler.

No new tests, no behavior change.

* WebProcess/Notifications/NotificationPermissionRequestManager.cpp:
(WebKit::NotificationPermissionRequestManager::NotificationPermissionRequestManager):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@182936 268f45cc-cd09-0410-ab3c-d52691b4dbfc