[BlackBerry] Crash running layout tests
https://bugs.webkit.org/show_bug.cgi?id=114503

Patch by Carlos Garcia Campos <cgarcia@igalia.com> on 2013-04-12
Reviewed by Xan Lopez.

Hit an assertion in ~GuardedPointerBase when DRT is
deleted. DumpRenderTree class derives from
BlackBerry::Platform::LayoutTestClient that derives from
BlackBerry::Platform::GuardedPointerBase, so the DRT pointer
should no be released with delete but with
BlackBerry::Platform::deleteGuardedObject().

* Api/WebPage.cpp:
(BlackBerry::WebKit::WebPagePrivate::~WebPagePrivate):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@148277 268f45cc-cd09-0410-ab3c-d52691b4dbfc