Make HTTP middleware easier to use

server/templates/middleware.go

 // Copyright 2015 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 templates
 
 import (
         "fmt"
         "net/http"
 
-        "github.com/julienschmidt/httprouter"
-        "golang.org/x/net/context"
-
-        "github.com/luci/luci-go/server/middleware"
+        "github.com/luci/luci-go/server/router"
 )
 
 // WithTemplates is middleware that lazily loads template bundle and injects it
 // into the context.
 //
 // Wrapper reply with HTTP 500 if templates can not be loaded. Inner handler
 // receives context with all templates successfully loaded.
-func WithTemplates(h middleware.Handler, b *Bundle) middleware.Handler {
-        return func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-                c = Use(c, b) // calls EnsureLoaded and initializes b.err inside
+func WithTemplates(b *Bundle) router.Middleware {
+        return func(c *router.Context, next router.Handler) {
+                c.Context = Use(c.Context, b) // calls EnsureLoaded and initializes b.err inside
                 if b.err != nil {
-                        http.Error(rw, fmt.Sprintf("Can't load HTML templates.\n%s", b.err), http.StatusInternalServerError)
+                        http.Error(c.Writer, fmt.Sprintf("Can't load HTML templates.\n%s", b.err), http.StatusInternalServerError)
                         return
                 }
-                h(c, rw, r, p)
+                next(c)
         }
 }