Disallow fullscreen from within <frame>, even with allowfullscreen

This was fixed once before in WebKit:
http://trac.webkit.org/changeset/84706

Unfortunately, webkitfullscreenallowed was the wrong attribute name
and it was added to the wrong <frame> element, so the test didn't
catch when this regressed some time between then and now.

The updated test has been verified to fail without this fix.

BUG=390041

Review URL: https://codereview.chromium.org/356303004

git-svn-id: svn://svn.chromium.org/blink/trunk@177204 bbb929c8-8fbe-4397-9dbb-9b2b20218538