[Sync] Clean up ModelType code.

components/sync/driver/model_association_manager.cc

 // Copyright 2014 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 "components/sync/driver/model_association_manager.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 30 matching lines @@
                        //  so we want to do it early.
     PREFERENCES, PRIORITY_PREFERENCES, EXTENSIONS, APPS, APP_LIST, ARC_PACKAGE,
     READING_LIST, THEMES, SEARCH_ENGINES, SESSIONS, APP_NOTIFICATIONS,
     DICTIONARY, FAVICON_IMAGES, FAVICON_TRACKING, PRINTERS,
     SUPERVISED_USER_SETTINGS, SUPERVISED_USER_SHARED_SETTINGS,
     SUPERVISED_USER_WHITELISTS, ARTICLES, WIFI_CREDENTIALS,
 };
 
 static_assert(arraysize(kStartOrder) ==
                   MODEL_TYPE_COUNT - FIRST_REAL_MODEL_TYPE,
-              "kStartOrder must have MODEL_TYPE_COUNT - "
-              "FIRST_REAL_MODEL_TYPE elements");
+              "When adding a new type, update kStartOrder.");
 
 // The amount of time we wait for association to finish. If some types haven't
 // finished association by the time, DataTypeManager is notified of the
 // unfinished types.
 const int64_t kAssociationTimeOutInSeconds = 600;
 
 DataTypeAssociationStats BuildAssociationStatsFromMergeResults(
     const SyncMergeResult& local_merge_result,
     const SyncMergeResult& syncer_merge_result,
     const base::TimeDelta& association_wait_time,
@@ skipping 356 matching lines @@
       // At least one type is not ready.
       return;
     }
   }
 
   notified_about_ready_for_configure_ = true;
   delegate_->OnAllDataTypesReadyForConfigure();
 }
 
 }  // namespace syncer