Refactor distributor API so that methods always get the Quest_Desc too.

dm/appengine/mutate/schedule_execution.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 mutate
 
 import (
         "fmt"
 
         "github.com/luci/gae/filter/txnBuf"
@@ skipping 62 matching lines @@
         }
 
         eid := dm.NewExecutionID(s.For.Quest, s.For.Id, a.CurExecution)
         e := model.MakeExecution(c, eid, q.Desc.DistributorConfigName, ver)
         e.TimeToStart = q.Desc.Meta.Timeouts.Start.Duration()
         e.TimeToRun = q.Desc.Meta.Timeouts.Run.Duration()
 
         exAuth := &dm.Execution_Auth{Id: eid, Token: e.Token}
 
         var distTok distributor.Token
-        distTok, e.TimeToStop, err = dist.Run(
-                distributor.NewTaskDescription(c, &q.Desc, exAuth, prevResult))
+        distTok, e.TimeToStop, err = dist.Run(&q.Desc, exAuth, prevResult)
         if e.TimeToStop <= 0 {
                 e.TimeToStop = q.Desc.Meta.Timeouts.Stop.Duration()
         }
         e.DistributorToken = string(distTok)
         if err != nil {
                 if errors.IsTransient(err) {
                         // tumble will retry us later
                         logging.WithError(err).Errorf(c, "got transient error in ScheduleExecution")
                         return
                 }
@@ skipping 20 matching lines @@
         if err = ds.Put(a, e); err != nil {
                 logging.WithError(err).Errorf(c, "putting attempt+execution")
         }
 
         return
 }
 
 func init() {
         tumble.Register((*ScheduleExecution)(nil))
 }