sync: Process 'control' data separately

sync/engine/sync_scheduler.cc

Index: sync/engine/sync_scheduler.cc
diff --git a/sync/engine/sync_scheduler.cc b/sync/engine/sync_scheduler.cc
index 199c5079062d10ab801f10973437022011fdd3c6..d06edc283d9ff61755ce0f6ac728cbe83bd7f8e7 100644
--- a/sync/engine/sync_scheduler.cc
+++ b/sync/engine/sync_scheduler.cc
@@ -550,6 +550,7 @@ void GetModelSafeParamsForTypes(ModelTypeSet types,
     ModelSafeRoutingInfo* result_routes,
     std::vector<ModelSafeWorker*>* result_workers) {
   bool passive_group_added = false;
+  bool control_group_added = false;
 
   typedef std::vector<ModelSafeWorker*>::const_iterator iter;
   for (ModelTypeSet::Iterator it = types.First();
@@ -571,6 +572,8 @@ void GetModelSafeParamsForTypes(ModelTypeSet types,
 
       if (group == GROUP_PASSIVE)
         passive_group_added = true;
+      if (group == GROUP_CONTROL)
+        control_group_added = true;
     } else {
         NOTREACHED();
     }
@@ -585,6 +588,14 @@ void GetModelSafeParamsForTypes(ModelTypeSet types,
     else
       NOTREACHED();
   }
+  if (control_group_added == false) {
+    iter it = std::find_if(current_workers.begin(), current_workers.end(),
+                           ModelSafeWorkerGroupIs(GROUP_CONTROL));
+    if (it != current_workers.end())
+      result_workers->push_back(*it);
+    else
+      NOTREACHED();
+  }
 }
 
 void SyncScheduler::ScheduleConfiguration(