Disallow infinite values for CSS numbers.

Infinite numerical values are never valid, so disallow them at parsing.

BUG=329006

Review URL: https://codereview.chromium.org/153353002

git-svn-id: svn://svn.chromium.org/blink/trunk@167047 bbb929c8-8fbe-4397-9dbb-9b2b20218538