Make HTTP middleware easier to use

appengine/cmd/dm/distributor/tq_handler.go

Index: appengine/cmd/dm/distributor/tq_handler.go
diff --git a/appengine/cmd/dm/distributor/tq_handler.go b/appengine/cmd/dm/distributor/tq_handler.go
index 218f1eb23dbdb5e4a8cbbfcd787eddbcb2695247..631dcde1ced11211c265b6bafee208d8ba0e84df 100644
--- a/appengine/cmd/dm/distributor/tq_handler.go
+++ b/appengine/cmd/dm/distributor/tq_handler.go
@@ -2,38 +2,38 @@
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package distributor
 
 import (
 	"net/http"
 	"net/url"
 	"strings"
 
-	"github.com/julienschmidt/httprouter"
 	"github.com/luci/luci-go/appengine/tumble"
 	"github.com/luci/luci-go/common/logging"
-	"golang.org/x/net/context"
+	"github.com/luci/luci-go/server/router"
 )
 
 const handlerPattern = "/tq/distributor/:cfgName"
 
 func handlerPath(cfgName string) string {
 	return strings.Replace(handlerPattern, ":cfgName", url.QueryEscape(cfgName), 1)
 }
 
 // TaskQueueHandler is the http handler that routes taskqueue tasks made with
 // Config.EnqueueTask to a distributor's HandleTaskQueueTask method.
 //
-// This requires that c already have a Registry installed via the WithRegistry
-// method.
-func TaskQueueHandler(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
+// This requires that ctx.Context already have a Registry installed via the
+// WithRegistry method.
+func TaskQueueHandler(ctx *router.Context) {
+	c, rw, r, p := ctx.Context, ctx.Writer, ctx.Request, ctx.Params
 	defer r.Body.Close()
 
 	cfgName := p.ByName("cfgName")
 	dist, _, err := GetRegistry(c).MakeDistributor(c, cfgName)
 	if err != nil {
 		logging.Fields{"error": err, "cfg": cfgName}.Errorf(c, "Failed to make distributor")
 		http.Error(rw, "bad distributor", http.StatusBadRequest)
 		return
 	}
 	notifications, err := dist.HandleTaskQueueTask(r)