Contour with heatmap coloring not behaving well on resize

[etpinard]

https://codepen.io/etpinard/pen/YbGapz - first reported on https://community.plot.ly/t/responsive-true-causes-styling-colors-to-disappear-on-resize/23311

[etpinard]

This bug appears fixed on the current master:

https://codepen.io/etpinard/pen/XwMmRe?editors=1010

I suspect the colorbar refactor PR #3786 fixed this thing