SkFontHost_mac.cpp#create_descriptor to handle nullptr familyName.

Currently create_descriptor will crash if handed a familyName which is
nullptr. Instead it should simply create a descriptor without a family name
and allow CoreText to resolve a default font. This further simplifies
default font handling on Mac.

BUG=skia:6196

Change-Id: I0a2d081240e4cb5bd51dd3516ea2595277055fe0
Reviewed-on: https://skia-review.googlesource.com/8071
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Ben Wagner <bungeman@google.com>
1 file changed