It is only necessary in a few places, and this inlining will
simplify the transition away from NodeLists.

Passes toolstash -cmp.

Change-Id: I4ee9b4bf56ffa04df23e20a0a83b302d36b33510
Reviewed-on: https://go-review.googlesource.com/20290Reviewed-by: Ian Lance Taylor <iant@golang.org>