Add support for Pull Queues to prod implementation.

service/taskqueue/raw_interface.go

 // Copyright 2015 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package taskqueue
 
 // RawCB is a simple callback for RawInterface.DeleteMulti, getting the error
 // for the attempted deletion.
 type RawCB func(error)
 
 // RawTaskCB is the callback for RawInterface.AddMulti, getting the added task
 // and an error.
 type RawTaskCB func(*Task, error)
 
 // RawStatsCB is the callback for RawInterface.Stats. It takes the statistics
 // object, as well as an error (e.g. in case the queue doesn't exist).
 type RawStatsCB func(*Statistics, error)
 
 // RawInterface is the full interface to the Task Queue service.
 type RawInterface interface {
         // AddMulti adds multiple tasks to the given queue, calling cb for each item.
         //
         // The task passed to the callback function will have all the default values
         // filled in, and will have the Name field populated, if the input task was
         // anonymous (e.g. the Name field was blank).
         AddMulti(tasks []*Task, queueName string, cb RawTaskCB) error
         DeleteMulti(tasks []*Task, queueName string, cb RawCB) error
 
+        Lease(maxTasks int, queueName string, leaseTime int) ([]*Task, error)
+        LeaseByTag(maxTasks int, queueName string, leaseTime int, tag string) ([]*Task, error)
+        ModifyLease(task *Task, queueName string, leaseTime int) error
+
         Purge(queueName string) error
 
         Stats(queueNames []string, cb RawStatsCB) error
 
         GetTestable() Testable
 }