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

scheduler/appengine/engine/internal/gen.go

Index: scheduler/appengine/engine/internal/gen.go
diff --git a/scheduler/appengine/engine/internal/gen.go b/scheduler/appengine/engine/internal/gen.go
new file mode 100644
index 0000000000000000000000000000000000000000..5fe2b05af52ad9824d6d3621e2deb765d1c82e67
--- /dev/null
+++ b/scheduler/appengine/engine/internal/gen.go
@@ -0,0 +1,18 @@
+// 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.
+
+//go:generate cproto -import-path=internal
+
+// Package internal contains internal structs used by the engine.
+package internal