XHR should fire 'abort' event when navigation interrupts a request.
https://bugs.webkit.org/show_bug.cgi?id=110867

Reviewed by Alexey Proskuryakov.

Adding a layout test to ensure that navigation-canceled XMLHttpRequests
fire an 'abort' event rather than an 'error' event.

* http/tests/xmlhttprequest/navigation-should-abort-expected.txt: Added.
* http/tests/xmlhttprequest/navigation-should-abort.html: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144163 268f45cc-cd09-0410-ab3c-d52691b4dbfc