[USS] Move GetAllNodes from backend to controller

components/sync/driver/data_type_controller.h

Index: components/sync/driver/data_type_controller.h
diff --git a/components/sync/driver/data_type_controller.h b/components/sync/driver/data_type_controller.h
index 7035b5dcb78b8dc994a0c4529f7368b64a008558..c331f638ea526dae45af4f5ca03bf50975b7b663 100644
--- a/components/sync/driver/data_type_controller.h
+++ b/components/sync/driver/data_type_controller.h
@@ -75,6 +75,9 @@ class DataTypeController
 
   typedef base::Callback<void(syncer::ModelType, syncer::SyncError)>
       ModelLoadCallback;
+  typedef base::Callback<void(const syncer::ModelType,
+                              std::unique_ptr<base::ListValue>)>
+      AllNodesCallback;
 
   typedef std::map<syncer::ModelType, scoped_refptr<DataTypeController>>
       TypeMap;
@@ -153,6 +156,8 @@ class DataTypeController
   // Returns true by default.
   virtual bool ReadyForStart() const;
 
+  virtual void GetAllNodes(const AllNodesCallback& callback) = 0;
+
  protected:
   friend class base::RefCountedDeleteOnMessageLoop<DataTypeController>;
   friend class base::DeleteHelper<DataTypeController>;