Crash in NavigationScheduler::schedule.

Crash in NavigationScheduler::schedule.
https://bugs.webkit.org/show_bug.cgi?id=78297

Reviewed by Adam Barth.

Source/WebCore:

Protect frame pointer and navigation scheduler when we stop the
load (when redirect is scheduled during a load). Also, dont fire
the navigation scheduler timer when we know that frameloader is
going away.

Test: http/tests/navigation/navigation-redirect-schedule-crash.html

* loader/NavigationScheduler.cpp:
(WebCore::NavigationScheduler::schedule):

LayoutTests:

* http/tests/navigation/navigation-redirect-schedule-crash-expected.txt: Added.
* http/tests/navigation/navigation-redirect-schedule-crash.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@107729 268f45cc-cd09-0410-ab3c-d52691b4dbfc