lilypond 2.3.16: ChordName extra-offset interpreted differently

[Matthias Neeracher]

In one of my .ly files, I had included the instruction

          \override ChordName #'extra-offset = #'(0.0 . -3.0)

and I noticed that this comes out differently in lilypond 2.3.16 than 
in earlier versions: The chords now ride
on the top staff line.

The file is at

http://homepage.mac.com/neeracher/lilypond-2_3_16-chord-bug.ly

2.3.16 output at

http://homepage.mac.com/neeracher/lilypond-2_3_16-chord-bug.pdf

Not sure if this is really a bug or just a legitimate change in 
interpretation.

Matthias