[ft] TakaoMincho japanese truetype font size problem in pango, cairo

[mihara]

Hi,I am developing a report system(output pdf) using pango,cairo,
TakaoMincho font(japanese truetype font).

It works fine ubuntu 14.04,but ubuntu 16.04 or later,string line extents differ 
from before.
It seems that pango font rendereing have a problem with font size.
I wrote small sample program.

https://github.com/yusukemihara/test_takao_mincho

It render same japansese strings repeatedly,smaller and smaller.
ubuntu 14.04 trusty(freetype-2.5.2),glyphs rendererd bit by bit smaller,
ubutun 16.10 yaketty(freetype-2.6.3),glyphs rendered same size at some lines.

see out.1404.pdf and out.1610.pdf.

https://github.com/yusukemihara/test_takao_mincho/blob/master/out.1404.pdf
https://github.com/yusukemihara/test_takao_mincho/blob/master/out.1610.pdf

What are the possible cause? I should what to do?

Thank you,
yusuke mihara