Homebrew/homebrew — pull request #35096 by beschoenen (2014-12-18 17:39:46+00:00)
Title: Added harfbuzz optional to fix spacing issues

Refer to this thread:
https://github.com/mpv-player/mpv/issues/1365
tldr: I had spacing issues with japanese characters in mpv and they were fixed by recompiling libass with harfbuzz