Restore ViewObject implementation for all Draft objects

In my tests the code works fine. Using @AIRCAP's instructions,  I have created a 'broken' file from draft_test_objects.FCStd.

src/Mod/Draft/draftobjects/ellipse.py

@@ -31,6 +31,7 @@ from PySide.QtCore import QT_TRANSLATE_NOOP
 
 import FreeCAD as App
 from draftobjects.base import DraftObject
+from draftutils import gui_utils
 from draftutils import params
 
 
@@ -38,7 +39,7 @@ class Ellipse(DraftObject):
     """The Circle object"""
 
     def __init__(self, obj):
-        super(Ellipse, self).__init__(obj, "Ellipse")
+        super().__init__(obj, "Ellipse")
 
         _tip = QT_TRANSLATE_NOOP("App::Property","Start angle of the elliptical arc")
         obj.addProperty("App::PropertyAngle", "FirstAngle", "Draft", _tip)
@@ -61,6 +62,10 @@ class Ellipse(DraftObject):
 
         obj.MakeFace = params.get_param("fillmode")
 
+    def onDocumentRestored(self, obj):
+        super().onDocumentRestored(obj)
+        gui_utils.restore_view_object(obj, vp_module="view_base", vp_class="ViewProviderDraft")
+
     def execute(self, obj):
         if self.props_changed_placement_only():
             obj.positionBySupport()