Make HTTP middleware easier to use

appengine/cmd/milo/buildbot/pubsub.go

Index: appengine/cmd/milo/buildbot/pubsub.go
diff --git a/appengine/cmd/milo/buildbot/pubsub.go b/appengine/cmd/milo/buildbot/pubsub.go
index 0f883fa30c9d74c8f5a1d4c121a453adffdc3628..d4d88df1de90584a66e698b1d21beef076b26bdf 100644
--- a/appengine/cmd/milo/buildbot/pubsub.go
+++ b/appengine/cmd/milo/buildbot/pubsub.go
@@ -3,29 +3,28 @@
 // that can be found in the LICENSE file.
 
 package buildbot
 
 import (
 	"bytes"
 	"compress/gzip"
 	"compress/zlib"
 	"encoding/base64"
 	"encoding/json"
-	"net/http"
 	"time"
 
 	"github.com/luci/gae/service/datastore"
 	"github.com/luci/luci-go/common/clock"
 	"github.com/luci/luci-go/common/iotools"
 	log "github.com/luci/luci-go/common/logging"
+	"github.com/luci/luci-go/server/router"
 
-	"github.com/julienschmidt/httprouter"
 	"golang.org/x/net/context"
 )
 
 var (
 	// subName is the name of the pubsub subscription that milo is expecting.
 	// TODO(hinoka): This should be read from luci-config.
 	subName = "projects/luci-milo/subscriptions/buildbot-public"
 )
 
 type pubSubMessage struct {
@@ -111,22 +110,23 @@ func unmarshal(
 			bm.Builds = append(bm.Builds, build)
 			slave.RunningbuildsMap[build.Buildername] = append(
 				slave.RunningbuildsMap[build.Buildername], build.Number)
 		}
 		slave.Runningbuilds = nil
 	}
 	return bm.Builds, bm.Master, nil
 }
 
 // PubSubHandler is a webhook that stores the builds coming in from pubsub.
-func PubSubHandler(
-	c context.Context, h http.ResponseWriter, r *http.Request, p httprouter.Params) {
+func PubSubHandler(ctx *router.Context) {
+	c, h, r := ctx.Context, ctx.Writer, ctx.Request
+
 	msg := pubSubSubscription{}
 	defer r.Body.Close()
 	dec := json.NewDecoder(r.Body)
 	if err := dec.Decode(&msg); err != nil {
 		log.WithError(err).Errorf(
 			c, "Could not decode message.  %s", err)
 		h.WriteHeader(200) // This is a hard failure, we don't want PubSub to retry.
 		return
 	}
 	if msg.Subscription != subName {