Make HTTP middleware easier to use

common/prpc/talk/helloworld/frontend/prpc.go

Index: common/prpc/talk/helloworld/frontend/prpc.go
diff --git a/common/prpc/talk/helloworld/frontend/prpc.go b/common/prpc/talk/helloworld/frontend/prpc.go
index a5904d9c8bbcf84497e966b1e7f479c4a8de9843..d011ab074361f38adf16e7608cc96ded19d40724 100644
--- a/common/prpc/talk/helloworld/frontend/prpc.go
+++ b/common/prpc/talk/helloworld/frontend/prpc.go
@@ -1,22 +1,20 @@
 // Copyright 2016 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package helloworld
 
 import (
-	"github.com/julienschmidt/httprouter"
-
 	"github.com/luci/luci-go/server/discovery"
-	"github.com/luci/luci-go/server/middleware"
 	"github.com/luci/luci-go/server/prpc"
+	"github.com/luci/luci-go/server/router"
 
 	"github.com/luci/luci-go/common/prpc/talk/helloworld/proto"
 )
 
-func InstallAPIRoutes(router *httprouter.Router, base middleware.Base) {
+func InstallAPIRoutes(r *router.Router, base router.MiddlewareChain) {
 	server := &prpc.Server{}
 	helloworld.RegisterGreeterServer(server, &greeterService{})
 	discovery.Enable(server)
-	server.InstallHandlers(router, base)
+	server.InstallHandlers(r, base)
 }