[USS] Change the place where SharedModelTypeProcessor got created

sync/api/model_type_service.h

 // Copyright 2015 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.
 
 #ifndef SYNC_API_MODEL_TYPE_SERVICE_H_
 #define SYNC_API_MODEL_TYPE_SERVICE_H_
 
 #include <string>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/memory/scoped_ptr.h"
 #include "sync/api/entity_change.h"
 #include "sync/api/entity_data.h"
 #include "sync/api/model_type_change_processor.h"
 #include "sync/api/sync_error.h"
 #include "sync/base/sync_export.h"
 
 namespace syncer_v2 {
 
 class DataBatch;
 class MetadataChangeList;
+class SharedModelTypeProcessor;
 
 // Interface implemented by model types to receive updates from sync via the
 // SharedModelTypeProcessor. Provides a way for sync to update the data and
 // metadata for entities, as well as the model type state.
 class SYNC_EXPORT ModelTypeService {
  public:
   typedef base::Callback<void(syncer::SyncError, scoped_ptr<DataBatch>)>
       DataCallback;
   typedef std::vector<std::string> ClientTagList;
+  typedef base::Callback<scoped_ptr<ModelTypeChangeProcessor>(
+      ModelTypeService* service)>
+      SharedProcessorFactory;
 
   ModelTypeService();
 
   virtual ~ModelTypeService();
 
   // Creates an object used to communicate changes in the sync metadata to the
   // model type store.
   virtual scoped_ptr<MetadataChangeList> CreateMetadataChangeList() = 0;
 
   // Perform the initial merge between local and sync data. This should only be
@@ skipping 32 matching lines @@
   virtual std::string GetClientTag(const EntityData& entity_data) = 0;
 
   // Overridable notification for when the processor is set. This is typically
   // when the service should start loading metadata and then subsequently giving
   // it to the processor.
   virtual void OnChangeProcessorSet() = 0;
 
   // TODO(skym): See crbug/547087, do we need all these accessors?
   ModelTypeChangeProcessor* change_processor() const;
 
-  void set_change_processor(
-      scoped_ptr<ModelTypeChangeProcessor> change_processor);
+  // The function will create SharedModelTypeProcessor and send
+  // notification(OnChangeProcessorSet).
+  ModelTypeChangeProcessor* InitializeProcessor(

[maxbogue, 2016/03/15 17:37:33]

The service might need to create the processor before the DTC exists. It needs
to receive the factory function in the constructor, and this function should
have the signature:

ModelTypeChangeProcessor* OnSyncStarting();

+      const SharedProcessorFactory& shared_processor_factory);
 
   void clear_change_processor();
 
  private:
-  // Recieves ownership in set_change_processor(...).
   scoped_ptr<ModelTypeChangeProcessor> change_processor_;
 };
 
 }  // namespace syncer_v2
 
 #endif  // SYNC_API_MODEL_TYPE_SERVICE_H_