Investigate performance regression in NYC Taxi selection example

[jonmmease]

There seems to be a performance regression with https://github.com/jonmmease/plotly_ipywidget_notebooks/blob/master/notebooks/nyc_taxi_selection.ipynb. There is a noticeable freeze after each interaction with the plot, even after things like changing the modebar tool. This only happens when the figure is displayed as a FigureWidget.

I have an unconfirmed suspicion that this has something to do with #1117. Perhaps we're serializing an unnecessary amount of data from JavaScript back to Python after plot interactions.