Use text size on Mac.

The current code assumes that text on Mac is freely scalable,
or at least that the text size is just a part of the transform.
However, it appears that application of the 'trak' table,
as well as other optical adjustments, may rely on the text size

This change passes the text size requested directly to CoreText.


Review URL:

Cherry-pick: be2284de556e7ec29489693093d42dc86b762645
3 files changed