Currently codepoint to glyph ID resolution is done through MinikinFont
interface. To support variation selector, use HarfBuzz API instead of
calling this interface since one of its implementation Skia doesn't
support variation selector.
On the other hand, we don't want to get glyph horizontal advance values
by HarfBuzz since HarfBuzz doesn't return correct values when the hinting
is active.
Thus, use ot_font as a parent font and override
glyph_h_advance/glyph_h_origin functions as is.
With this change, MinikinFont::GetGlyph is no longer necessary but not
removing in this CL for easy reverting since removing interface requires
multi-repository commit.
This is a base work of b/11256006 and this patch doesn't provide any
user visible changes.
Bug: 11256006
Change-Id: I061172c0b674bb649ce8bc013ffecf38708bdc41
0345da636e