This cleanup was proposed in CL 148937. The branch is already ended with
a continue, so remove continues from subbranches and use an else-if.

Change-Id: Iaf6eb57afc84e25862f99a342f5824e315bcdcb7
Reviewed-on: https://go-review.googlesource.com/c/148922Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>