Fix occasional blank video with poster attribute.

        * ChangeLog:
        * html/HTMLMediaElement.cpp:
        (WebCore::HTMLMediaElement::load):
        (WebCore::HTMLMediaElement::didRestoreFromCache):
        Just calling updateFromElement() does the right thing for both poster image and video.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@27659 268f45cc-cd09-0410-ab3c-d52691b4dbfc