Horizontal scrolling no enable since updating Jupyterlab to 3.0.0

首先，在 JupyterLab 3.0 中使用报告的 ipympl 0.5.8 和 ipywidgets 7.6.2 版本，通过创建一个宽度超过浏览器窗口的图表来复现缺失的水平滚动条。将 widget 的输出与 issue 中描述的宽 pandas dataframe 行为进行比较。当宽的 ipympl 图表再次提供水平滚动条时，即表示完成。

Describe the issue

For graphs wider than the browser window, the ipympl widget used to show an horizontal scroll bar at the end of the output. It does not show anymore since updating Jupyterlab to 3.0.0.
I supposed this is a ipympl issue since eg. wide pandas dataframes still show the horitonzal scrollbar.

Versions

 3.7.9 | packaged by conda-forge | (default, Dec  9 2020, 21:08:20)
[GCC 9.3.0]
ipympl version: 0.5.8
jupyter core     : 4.7.0
jupyter-notebook : 6.1.6
qtconsole        : 5.0.1
ipython          : 7.19.0
ipykernel        : 5.4.2
jupyter client   : 6.1.7
jupyter lab      : 3.0.0
nbconvert        : 6.0.7
ipywidgets       : 7.6.2
nbformat         : 5.0.8
traitlets        : 5.0.5
Config option `kernel_spec_manager_class` not recognized by `ListNBExtensionsApp`.
Known nbextensions:
  config dir: /home/picardgh/.jupyter/nbconfig
    notebook section
      jupyter-js-widgets/extension  enabled
      - Validating: OK
  config dir: /home/picardgh/anaconda3/etc/jupyter/nbconfig
    notebook section
      jupyter-matplotlib/extension  enabled
      - Validating: OK
      nbresuse/main  enabled
      - Validating: OK
      plotlywidget/extension  enabled
      - Validating: OK
      jupyter-js-widgets/extension  enabled
      - Validating: OK
      nbdime/index disabled
      qgrid/extension  enabled
      - Validating: OK
    tree section
      ipyparallel/main  enabled
      - Validating: OK