Apparently the use of [UIFont systemFontOfSize:10] familyName] to get
a default font family name is a bad idea. Presumably the return value
from this, ".SF UI Text", is matched against the list of font family
names enumerated from the system. (The "SF" apparently stands for "San
Francisco".) That ".SF UI Text" is not among them, so maybe vcl
chooses some arbitrary other font instead that happens to be a serif
one? If we instead use "Helvetica", at least we get a sans-serif font,
even if it doesn't match the system UI font exactly.

Change-Id: I7ff39d8e7893ce3c27f3f12d227f87209bbc7952