histogram2dcontour with heatmap coloring loses color on responsive resize

[jonmmease]

Originally reported in plotly/plotly.py#1573

When a histogram2dcontour trace with contour.coloring: 'heatmap' is displayed with a config of responsive: true, it loses its coloring on resize.

CodePen: https://codepen.io/jonmmease/pen/KLQWOO?editors=1010

var x = [0, 1, 1];
var y = [0, 1, 1];

var data = [
  {
    x: x,
    y: y,
    type: 'histogram2dcontour',
    contours: {coloring: 'heatmap'}
  }
];
Plotly.newPlot('graph', data, {}, {responsive:true}); 

[etpinard]

Fixed in master https://codepen.io/etpinard/pen/RmQMrz?editors=1010

Duplicate of #3858