[Sync] Convert DTCs to be not RefCounted and NonThreadSafe.

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 244 matching lines @@
       configure_status_ = DataTypeManager::ABORTED;
     DVLOG(1) << "ModelAssociationManager: Calling OnModelAssociationDone";
     ModelAssociationDone(IDLE);
   } else {
     DCHECK(associating_types_.Empty());
     DCHECK(requested_types_.Empty());
     state_ = IDLE;
   }
 }
 
-void ModelAssociationManager::ModelLoadCallback(syncer::ModelType type,
-                                                syncer::SyncError error) {
+void ModelAssociationManager::ModelLoadCallback(
+    syncer::ModelType type,
+    const syncer::SyncError& error) {
   DVLOG(1) << "ModelAssociationManager: ModelLoadCallback for "
            << syncer::ModelTypeToString(type);
 
   if (error.IsSet()) {
     syncer::SyncMergeResult local_merge_result(type);
     local_merge_result.set_error(error);
     TypeStartCallback(type, base::TimeTicks::Now(),
                       DataTypeController::ASSOCIATION_FAILED,
                       local_merge_result, syncer::SyncMergeResult(type));
     return;
@@ skipping 140 matching lines @@
       // At least one type is not ready.
       return;
     }
   }
 
   notified_about_ready_for_configure_ = true;
   delegate_->OnAllDataTypesReadyForConfigure();
 }
 
 }  // namespace sync_driver