avoid accessing app.widgets/_active_widgets entirely

* need to check if this adds any performance overhead

jdaviz/app.py

@@ -1162,9 +1162,6 @@ def vue_relayout(self, *args, **kwargs):
  """
  Forces any rendered ``Bqplot`` instances to resize themselves.
  """
- def get_widget(ipymodel):
- return getattr(self, '_active_widgets', self.widgets).get(ipymodel)
-
  def resize(stack_items):
  for stack in stack_items:
  for viewer_item in stack.get('viewers'):
@@ -1182,7 +1179,7 @@ def resize(stack_items):
  # resize tray items
  for tray_item in self.state.tray_items:
  # access the actual plugin object (there is no store for plugins)
- tray_obj = get_widget(tray_item['widget'].split('IPY_MODEL_')[1])
+ tray_obj = widget_serialization['from_json'](tray_item['widget'], None)
  for bqplot_fig in tray_obj.bqplot_figs_resize:
  bqplot_fig.layout.height = '99.9%'
  bqplot_fig.layout.height = '100%'