image: fix build accidentally deleted one method TBR=rsc
image: fix build
accidentally deleted one method
TBR=rsc

R=rsc
CC=golang-dev
http://codereview.appspot.com/4438090

pombredanne/go-deleteme,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,apparentlymart/golang,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,gnanderson/go,apparentlymart/golang,tv42/old-go,apparentlymart/golang,dsriram/golang,tv42/old-go,gnanderson/go,apparentlymart/golang,ssrl/go,ssrl/go,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,apparentlymart/golang,ssrl/go,ssrl/go,dsriram/golang,dsriram/golang,gnanderson/go,tv42/old-go,dsriram/golang,ssrl/go,tv42/old-go,ssrl/go,dsriram/golang,ssrl/go,pombredanne/go-deleteme,tv42/old-go,dsriram/golang,dsriram/golang,gnanderson/go,pombredanne/go-deleteme,gnanderson/go