unmounting/remounting dcc.Graphs > 16 times with WebGL children results in WebGL contexts warning

[wbrgss]

Console warning: WARNING: Too many active WebGL contexts. Oldest context will be lost.

The "oldest" WebGL graph will be un-rendered:

Dash app used to demo this bug (same as in #534)

• Using Chromium Version 73.0.3683.86 (Official Build) Built on Ubuntu , running on Ubuntu 18.04 (64-bit)
• Using Dash 0.41.0

import dash
import dash_html_components as html
import dash_core_components as dcc

app = dash.Dash(__name__)

app.layout = html.Div(children=[
    html.Div([
        # without the fix in this PR, this graph will disappear after clicking
        # graphs back and forth ~8 times
        dcc.Graph(
            id='example-graph-ex',
            figure={
                'data': [
                    {'x': [1, 2, 3], 'y': [4, 1, 2],
                        'type': 'scattergl', 'name': 'SF'},
                    {'x': [1, 2, 3], 'y': [2, 4, 5],
                     'type': 'scattergl', 'name': u'Montréal'},
                ]
            }
        )
    ]),
    dcc.Tabs(id="tabs", children=[
        dcc.Tab(label='Tab one', children=[
            html.Div([
                dcc.Graph(
                    id='example-graph',
                    figure={
                        'data': [
                            {'x': [1, 2, 3], 'y': [4, 1, 2],
                                'type': 'scattergl', 'name': 'SF'},
                            {'x': [1, 2, 3], 'y': [2, 4, 5],
                             'type': 'scattergl', 'name': u'Montréal'},
                        ]
                    }
                )
            ])
        ]),
        dcc.Tab(label='Tab two', children=[
                dcc.Graph(
                    id='example-graph-1',
                    figure={
                        'data': [
                            {'x': [1, 2, 3], 'y': [1, 4, 1],
                                'type': 'scattergl', 'name': 'SF'},
                            {'x': [1, 2, 3], 'y': [1, 2, 3],
                             'type': 'scattergl', 'name': u'Montréal'},
                        ]
                    }
                )
        ]),
        dcc.Tab(label='Tab three', children=[
                dcc.Graph(
                    id='example-graph-2',
                    figure={
                        'data': [
                            {'x': [1, 2, 3], 'y': [2, 4, 3],
                                'type': 'scattergl', 'name': 'SF'},
                            {'x': [1, 2, 3], 'y': [5, 4, 3],
                             'type': 'scattergl', 'name': u'Montréal'},
                        ]
                    }
                )
        ]),
    ])
])


if __name__ == '__main__':
    app.run_server(debug=True)

[wbrgss]

Seems to be fixed as of dash==0.43.0rc3 — keeping this open until it's released & I can confirm