font-variant should not allow "all" outside of @font-face rules.

c.f.
- spec: http://www.w3.org/TR/CSS2/fonts.html#propdef-font-variant

- WebKit commit: http://trac.webkit.org/changeset/34879

BUG=363631
TEST=fast/css/font-variant-with-all.html

Review URL: https://codereview.chromium.org/246213005

git-svn-id: svn://svn.chromium.org/blink/trunk@173758 bbb929c8-8fbe-4397-9dbb-9b2b20218538