Don’t buffer attributes that are being set from the kernel unless they changed.
Don’t buffer attributes that are being set from the kernel unless they changed.

Fixes #1195
jupyter-widgets/ipywidgets,ipython/ipywidgets,jupyter-widgets/ipywidgets,jupyter-widgets/ipywidgets,jupyter-widgets/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,ipython/ipywidgets,SylvainCorlay/ipywidgets,SylvainCorlay/ipywidgets,SylvainCorlay/ipywidgets,ipython/ipywidgets,SylvainCorlay/ipywidgets