misc/emacs: send correct content-length to the playground
misc/emacs: send correct content-length to the playground

R=adonovan
CC=golang-dev
https://codereview.appspot.com/14548049

Committer: Alan Donovan <7069e9552f9d110b0a0f326b96f22f63fb99dfc1@google.com>

wesolows/golang,wesolows/golang-old,wesolows/golang,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,wesolows/golang-old,wesolows/golang,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang,firebitsbr/golang-old,wesolows/golang-old,firebitsbr/golang-old,firebitsbr/golang-old,wesolows/golang