[Sync] Make syncer commands avoid posting tasks on threads with no work to do

chrome/browser/sync/engine/sync_scheduler.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/sync/engine/sync_scheduler.h"
 
 #include <algorithm>
 #include <cstring>
 
 #include "base/bind.h"
@@ skipping 744 matching lines @@
       SDVLOG(2) << "Dropping a nudge in "
                 << "DoSyncSessionJob because another nudge was scheduled";
       return;  // Another nudge must have been scheduled in in the meantime.
     }
     pending_nudge_.reset();
 
     // Create the session with the latest model safe table and use it to purge
     // and update any disabled or modified entries in the job.
     scoped_ptr<SyncSession> session(CreateSyncSession(job.session->source()));
 
-    job.session->RebaseRoutingInfoWithLatest(session.get());
+    job.session->RebaseRoutingInfoWithLatest(*session);
   }
   SDVLOG(2) << "DoSyncSessionJob with "
             << SyncSessionJob::GetPurposeString(job.purpose) << " job";
 
   SyncerStep begin(SYNCER_END);
   SyncerStep end(SYNCER_END);
   SetSyncerStepsForPurpose(job.purpose, &begin, &end);
 
   bool has_more_to_sync = true;
   while (ShouldRunJob(job) && has_more_to_sync) {
@@ skipping 411 matching lines @@
 
 #undef SDVLOG_LOC
 
 #undef SDVLOG
 
 #undef SLOG
 
 #undef ENUM_CASE
 
 }  // browser_sync