outlineCompiler: round head values that may be float in UFO

[moyogo]

No description provided.

[anthrotype]

@moyogo although I don't see how you're hitting floats for the head xMin, yMin, etc.
Given the way we calculate self.fontBoundingBox, i.e. as the unionRect of all the glyph's controlPointBounds, it should not be necessary to call round again.
We are already calling round inside makeGlyphsBoundingBoxes:
https://github.com/moyogo/ufo2ft/blob/a33d8851a128aa61a454bcf26ea2468aaa9500ff/Lib/ufo2ft/outlineCompiler.py#L120
I guess calling it again doesn't hurt, but I was just curious to understand.

[moyogo]

Good point, we don’t need to round the bounding box values, just the unitsPerEm.