The behavior hasn't changed much yet: all languages are ignored for
rendering text, except the very first supported language.
Change-Id: I1695fb985927ae5e28e4f59c1b531e4993af8688
This CL introduces new method hasVariationSelector into FontFamily but it
is not used in production code. So no behavior changes are expected.
This CL contains the following changes:
- Introduce hasVariationSelector which returns true if the corresponding
font has a glyph for a code point and variation selector pair.
- Introduce purgeHbFontCache since hb_face_t won't be released by
keeping hb_font_t.
- Introduce unit tests with self-built font.
Change-Id: I659a6d03d9ec446b409e1fba2758452abb9f44fa
