Should update FontFaceCache version when updating generic font-family settings.

BUG=381612
TEST=fast/text/update-sans-serif-and-recalc-style.html

Review URL: https://codereview.chromium.org/335393002

git-svn-id: svn://svn.chromium.org/blink/trunk@176327 bbb929c8-8fbe-4397-9dbb-9b2b20218538