https://bugs.webkit.org/show_bug.cgi?id=29510
        Active DOM objects should be suspended while a modal dialog is displayed

        * manual-tests/js-timers-beneath-modal-dialog.html: Added a test for JS timers.

        * page/PageGroupLoadDeferrer.cpp:
        (WebCore::PageGroupLoadDeferrer::PageGroupLoadDeferrer):
        (WebCore::PageGroupLoadDeferrer::~PageGroupLoadDeferrer):
        Match other platforms, and make Mac also suspend active DOM objects. Since a page that
        currently displays a modal dialog cannot go into page cache, there is no danger of suspending
        an object twice.        



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@48540 268f45cc-cd09-0410-ab3c-d52691b4dbfc