HTMLEmbedObject should match HTMLObjectElement by stopping any load when it is remove...

HTMLEmbedObject should match HTMLObjectElement by stopping any load when it is removed from beforeload
https://bugs.webkit.org/show_bug.cgi?id=74360

Reviewed by Adam Barth.

Source/WebCore:

Neither of these !renderer() checks is strictly necessary since requestObject()
makes the same check.  However requestObject() asserts before it makes that
check, so it makes sense to add the check to HTMLEmebedObject instead of
removing the check from HTMLObjectElement.
I also moved the protect RefPtr to before the beforeload dispatch since
beforeload can remove the whole DOM element (as this test does) and
thus I beleive the renderer() check could be checking free'd memory.

Updated fast/dom/beforeload/remove-flash-in-beforeload-listener.html to test
<embed> as well as <object>.

* html/HTMLEmbedElement.cpp:
(WebCore::HTMLEmbedElement::updateWidget):
* html/HTMLObjectElement.cpp:
(WebCore::HTMLObjectElement::updateWidget):

LayoutTests:

Test <embed> as well as <object> in this test.

* fast/dom/beforeload/remove-flash-in-beforeload-listener.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105938 268f45cc-cd09-0410-ab3c-d52691b4dbfc