Fix ZWJ not working for Indic fonts

This is a fix for bug 15185229 ZWJ not working in Sinhala and Kannada.

Indic fonts (unlike Arabic) require the entire string, including ZWJ,
to be passed to Harfbuzz; it's not enough for the ZWJ to be present in
the context. The solution is to be "sticky" in font itemization,
continuing to use the same font as long as it has Unicode coverage.

Change-Id: I7673bc56fbda09f1e1a4582e8d88342343b706f1
2 files changed
tree: 3a8187ce949110cb402cf4205eaa566cae88ce99
  1. include/
  2. libs/
  3. sample/