Add a task queue task router to reduce amount of boilerplate.

scheduler/appengine/engine/tq/globals.go

+// Copyright 2017 The LUCI Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tq
+
+import (
+        "github.com/golang/protobuf/proto"
+        "github.com/luci/gae/service/taskqueue"
+        "golang.org/x/net/context"
+)
+
+// DefaultDispatcher is global task dispatcher.
+var DefaultDispatcher = Dispatcher{}
+
+// RegisterTask registers the task in default dispatcher.
+func RegisterTask(prototype proto.Message, cb Handler, queue string, opts *taskqueue.RetryOptions) {
+        DefaultDispatcher.RegisterTask(prototype, cb, queue, opts)
+}
+
+// AddTask submits a task through default dispatcher.
+func AddTask(c context.Context, task Task) error {
+        return DefaultDispatcher.AddTask(c, task)
+}