Resize callback not working

Start by running the supplied Jupyter Notebook example with ipympl 0.7.0 and compare the resize_event callback with draw_event. Trace the fig.canvas.mpl_connect entry point through the notebook integration to identify why resizing does not reach the callback. Done means the example prints action when the figure is resized, with the existing callback behavior preserved.

Describe the issue

I am having an issue specifically with the Resize callback. The other callback options appear to work as expected. For example replacing 'resize_event' with 'draw_event' in the code block below gives no issues.

import matplotlib.pyplot as plt
import numpy as np
from ipywidgets import Output
%matplotlib widget

output = Output()

@output.capture()
def key_event(event):
    print('action')

fig, ax = plt.subplots()
ax.plot(np.random.rand(10))
fig.canvas.mpl_connect('resize_event', key_event)

display(output)

Versions

3.6.8 (default, Jan 14 2019, 11:02:34) 
[GCC 8.0.1 20180414 (experimental) [trunk revision 259383]]
ipympl version: 0.7.0
jupyter core     : 4.5.0
jupyter-notebook : 6.0.1
qtconsole        : not installed
ipython          : 7.7.0
ipykernel        : 5.1.2
jupyter client   : 5.3.1
jupyter lab      : 1.0.9
nbconvert        : 5.6.0
ipywidgets       : 7.6.3
nbformat         : 4.4.0
traitlets        : 4.3.2
Known nbextensions:
  config dir: /usr/local/etc/jupyter/nbconfig
    notebook section
      ipyvolume/extension  enabled
      - Validating: OK
      jupyter-datawidgets/extension  enabled
      - Validating: OK
      jupyter-matplotlib/extension  enabled
      - Validating: OK
      jupyter-threejs/extension  enabled
      - Validating: OK
      jupyter-webrtc/extension  enabled
      - Validating: OK
      jupyter-js-widgets/extension  enabled
      - Validating: OK
    tree section
      ipyparallel/main  enabled
      - Validating: OK
JupyterLab v1.0.9
Known labextensions:
   app dir: /usr/local/share/jupyter/lab
        jupyter-threejs v2.3.0  enabled  OK
        jupyterlab-datawidgets v7.0.0  enabled  OK