chord names and pickup measures

[rif]

I'm laying out a jazz sheet that has an eigth note "pickup" before
measure 1.  I would like to have the first chord name aligned with
measure 1, NOT with the pickup.  Any ideas how to do that?  I've tried
messing around with \once \override ??? #'extra-offset, but I'm not sure
what to put in for ??? (I've tried a few things, but lilypond just says
that's "not a grob" and ignores.)

Cheers,

rif