[Sync] Make directory types registration explicit in ModelTypeRegistry

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 151 matching lines @@
   for (size_t i = 0; i < arraysize(kStartOrder); i++) {
     ModelType type = kStartOrder[i];
     if (!desired_types_.Has(type))
       continue;
 
     DCHECK(controllers_->find(type) != controllers_->end());
     DataTypeController* dtc = controllers_->find(type)->second.get();
     if (dtc->state() == DataTypeController::NOT_RUNNING) {
       DCHECK(!loaded_types_.Has(dtc->type()));
       DCHECK(!associated_types_.Has(dtc->type()));
+      delegate_->OnSingleDataTypeWillStart(dtc->type());

[maxbogue, 2017/01/18 01:24:11]

Do you need to thread this call through DataTypeManagerImpl? It's just accessing
the DTC and calling BeforeLoadModels on it, and the ModelAssociationManager
could do that right here.

[pavely, 2017/01/18 20:18:07]

All the code that deals with registering types is in DTMI, I didn't want to
pollute MAM with just this one call. And to be honest I think LoadModels doesn't
belong in MAM either.

       dtc->LoadModels(base::Bind(&ModelAssociationManager::ModelLoadCallback,
                                  weak_ptr_factory_.GetWeakPtr()));
     }
   }
   NotifyDelegateIfReadyForConfigure();
 }
 
 void ModelAssociationManager::StartAssociationAsync(
     const ModelTypeSet& types_to_associate) {
   DCHECK_EQ(INITIALIZED, state_);
@@ skipping 226 matching lines @@
       // At least one type is not ready.
       return;
     }
   }
 
   notified_about_ready_for_configure_ = true;
   delegate_->OnAllDataTypesReadyForConfigure();
 }
 
 }  // namespace syncer