Test for https://bugs.webkit.org/show_bug.cgi?id=65270. 
Resource load delegate should be able to block poster loading.


Testing before setting poster
EXPECTED (video.clientWidth == '300') OK
EXPECTED (video.clientHeight == '150') OK

Test after setting poster
EXPECTED (video.clientWidth == '300') OK
EXPECTED (video.clientHeight == '150') OK
END OF TEST

