Fixes #580.
R=adg
CC=golang-dev
https://golang.org/cl/207086
// Objects implementing the Handler interface can be
// registered to serve a particular path or subtree
// in the HTTP server.
+//
+// ServeHTTP should write reply headers and data to the Conn
+// and then return. Returning signals that the request is finished
+// and that the HTTP server can move on to the next request on
+// the connection.
type Handler interface {
ServeHTTP(*Conn, *Request)
}