[Sync] Make BackendMigrator not wait for full sync cycles

chrome/browser/sync/engine/syncer_proto_util.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/syncer_proto_util.h"
 
 #include "base/format_macros.h"
 #include "base/stringprintf.h"
 #include "chrome/browser/sync/engine/net/server_connection_manager.h"
 #include "chrome/browser/sync/engine/syncer.h"
@@ skipping 75 matching lines @@
 void SyncerProtoUtil::HandleMigrationDoneResponse(
   const sync_pb::ClientToServerResponse* response,
   sessions::SyncSession* session) {
   LOG_IF(ERROR, 0 >= response->migrated_data_type_id_size())
       << "MIGRATION_DONE but no types specified.";
   syncable::ModelTypeSet to_migrate;
   for (int i = 0; i < response->migrated_data_type_id_size(); i++) {
     to_migrate.insert(syncable::GetModelTypeFromExtensionFieldNumber(
         response->migrated_data_type_id(i)));
   }
+  // TODO(akalin): This should be a set union.
   session->status_controller()->set_types_needing_local_migration(to_migrate);
 }
 
 // static
 bool SyncerProtoUtil::VerifyResponseBirthday(syncable::Directory* dir,
     const ClientToServerResponse* response) {
 
   std::string local_birthday = dir->store_birthday();
 
   // TODO(lipalani) : Remove this check here. When the new implementation
@@ skipping 399 matching lines @@
 std::string SyncerProtoUtil::ClientToServerResponseDebugString(
     const sync_pb::ClientToServerResponse& response) {
   // Add more handlers as needed.
   std::string output;
   if (response.has_get_updates())
     output.append(GetUpdatesResponseString(response.get_updates()));
   return output;
 }
 
 }  // namespace browser_sync