[Sync] Make BackendMigrator not wait for full sync cycles

chrome/browser/sync/glue/sync_backend_registrar.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/glue/sync_backend_registrar.h"
 
 #include <algorithm>
 
 #include "base/compiler_specific.h"
 #include "base/logging.h"
@@ skipping 119 matching lines @@
     // routing_info, if it does not already exist.
     if (routing_info_.count(*it) == 0) {
       routing_info_[*it] = GROUP_PASSIVE;
       newly_added_types.insert(*it);
     }
   }
   for (syncable::ModelTypeSet::const_iterator it = types_to_remove.begin();
        it != types_to_remove.end(); ++it) {
     routing_info_.erase(*it);
   }
+
+  VLOG(1) << "Adding types " << syncable::ModelTypeSetToString(types_to_add)
+          << " (with newly-added types "
+          << syncable::ModelTypeSetToString(newly_added_types)
+          << ") and removing types "
+          << syncable::ModelTypeSetToString(types_to_remove)
+          << " to get new routing info "
+          << ModelSafeRoutingInfoToString(routing_info_);
+
   return newly_added_types;
 }
 
 void SyncBackendRegistrar::StopOnUIThread() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   DCHECK(!stopped_on_ui_thread_);
   ui_worker_->Stop();
   stopped_on_ui_thread_ = true;
 }
 
@@ skipping 88 matching lines @@
 }
 
 bool SyncBackendRegistrar::IsCurrentThreadSafeForModel(
     syncable::ModelType model_type) const {
   lock_.AssertAcquired();
   return IsOnThreadForGroup(GetGroupForModelType(model_type, routing_info_));
 }
 
 }  // namespace browser_sync