Use Skia for WebFonts when GDI_FONTS_ON_WINDOWS is un-enabled.

R=eae@chromium.org

Review URL: https://codereview.chromium.org/23602006

git-svn-id: svn://svn.chromium.org/blink/trunk@156881 bbb929c8-8fbe-4397-9dbb-9b2b20218538