This will enable me to test the new API in unit tests without depending on HarfBuzz (after https://crrev.com/2322403002 lands). TBR= BUG=skia:5434 Review-Url: https://codereview.chromium.org/2332473003
also, re-enable warnings. motivation: used by me for PDF testing. BUG=skia: GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2201153002 Review-Url: https://codereview.chromium.org/2201153002