[USS] Change the place where SharedModelTypeProcessor got created

sync/api/model_type_service.h

Index: sync/api/model_type_service.h
diff --git a/sync/api/model_type_service.h b/sync/api/model_type_service.h
index bba4211ffe47af84dfff1f733272dad5d594dcca..683a62e920348a1fb721874c6698842d71b5aa7f 100644
--- a/sync/api/model_type_service.h
+++ b/sync/api/model_type_service.h
@@ -20,6 +20,7 @@ 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
@@ -29,6 +30,9 @@ class SYNC_EXPORT ModelTypeService {
   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();
 
@@ -81,13 +85,14 @@ class SYNC_EXPORT ModelTypeService {
   // 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_;
 };