Use NewScriptState in core/css/FontFace

This CL replaces ScriptState with NewScriptState in core/css/FontFace.

BUG=357144

Review URL: https://codereview.chromium.org/228003003

git-svn-id: svn://svn.chromium.org/blink/trunk@171042 bbb929c8-8fbe-4397-9dbb-9b2b20218538