SkFontMgr_FontConfigInterface create typeface from FontParameters.

This implements
SkFontMgr_FontConfigInterface::onCreateFromStream(SkStreamAsset*, const FontParameters&)
and makes the changes needed to support it. This will allow Chromium to
create variation fonts from data.

BUG=skia:5697
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2296843002

Review-Url: https://codereview.chromium.org/2296843002
2 files changed