Source/WebCore: Crash in WebCore::FrameLoader::checkCompleted()
https://bugs.webkit.org/show_bug.cgi?id=110237

Reviewed by Abhishek Arya.

Test: http/tests/misc/delete-frame-during-readystatechange.html

* loader/FrameLoader.cpp:
(WebCore::FrameLoader::checkCompleted): Protect before setReadyState() is called.

LayoutTests: Test for https://bugs.webkit.org/show_bug.cgi?id=110237

Reviewed by Abhishek Arya.

* http/tests/misc/delete-frame-during-readystatechange-expected.txt: Added.
* http/tests/misc/delete-frame-during-readystatechange.html: Added.
* http/tests/misc/resources/delete-frame-during-readystatechange-frame.html: Added.
* http/tests/misc/resources/empty.ogv: Added.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@143514 268f45cc-cd09-0410-ab3c-d52691b4dbfc