Simplify slice/map literal expressions.
Caught with gofmt -d -s, fixed with gofmt -w -s

Change-Id: Iefd5f263c4f89a81da9427a7b9d97f13c35ab64f
Reviewed-on: https://go-review.googlesource.com/13838Reviewed-by: Andrew Gerrand <adg@golang.org>