Make HTTP middleware easier to use

appengine/cmd/dm/distributor/pubsub.go

Index: appengine/cmd/dm/distributor/pubsub.go
diff --git a/appengine/cmd/dm/distributor/pubsub.go b/appengine/cmd/dm/distributor/pubsub.go
index 65df41215b52bf74bfeee8f524483f01ce183ed7..a4cf5b4eea720029142d62e81ad0a920a6f2e4c9 100644
--- a/appengine/cmd/dm/distributor/pubsub.go
+++ b/appengine/cmd/dm/distributor/pubsub.go
@@ -4,37 +4,38 @@
 
 package distributor
 
 import (
 	"encoding/json"
 	"fmt"
 	"net/http"
 	"strconv"
 	"time"
 
-	"github.com/julienschmidt/httprouter"
 	"github.com/luci/luci-go/appengine/tumble"
 	"github.com/luci/luci-go/common/api/dm/service/v1"
 	"github.com/luci/luci-go/common/logging"
+	"github.com/luci/luci-go/server/router"
 	"github.com/luci/luci-go/server/tokens"
 	"golang.org/x/net/context"
 )
 
 const notifyTopicSuffix = "dm-distributor-notify"
 
-// PubsubReciever is the HTTP handler that processes incoming pubsub events
+// PubsubReceiver is the HTTP handler that processes incoming pubsub events
 // delivered to topics prepared with TaskDescription.PrepareTopic, and routes
 // them to the appropriate distributor implementation's HandleNotification
 // method.
 //
 // It requires that a Registry be installed in c via WithRegistry.
-func PubsubReciever(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
+func PubsubReceiver(ctx *router.Context) {
+	c, rw, r := ctx.Context, ctx.Writer, ctx.Request
 	defer r.Body.Close()
 
 	type PubsubMessage struct {
 		Attributes map[string]string `json:"attributes"`
 		Data       []byte            `json:"data"`
 		MessageID  string            `json:"message_id"`
 	}
 	type PubsubPushMessage struct {
 		Message      PubsubMessage `json:"message"`
 		Subscription string        `json:"subscription"`