performance issues between 0.28.0 and 0.32.0 - support plotly.js immutable mode

[chriddyp]

Repro example produced here: https://community.plot.ly/t/dash-core-component-performance-issues-on-mapbox-graphs-between-versions/14821/6

[chriddyp]

Still seems like it's an issue: https://community.plot.ly/t/dash-core-component-performance-issues-on-mapbox-graphs-between-versions/14821/8?u=chriddyp

[rockg]

I was able to pinpoint this performance regression between dcc versions 30.1 and 30.2 which narrows it down considerably. I believe that this line is the culprit which is creating a deep copy of the layout which can be large when one has a lot of geojson data. I see that this was put in to solve a resize issue and wonder if there are other alternatives. Curious to hear your thoughts @valentijnnieman and @chriddyp.

[rockg]

I built master and removed clone and the performance is back to 30.1 levels so the root cause is verified.

[alexcjohnson]

A full deep clone is certainly overkill for the intended fix (original PR #279), though considering data #287 and all the other places plotly.js might mutate layout, I suspect it would be easier to just implement a plotly.js immutable mode plotly/plotly.js#2389 than to figure out (and maintain) a safe-yet-fast copy operation here.

[chriddyp]

Another community post to follow-up on when this gets fixed one way or another https://community.plot.ly/t/mapbox-map-loads-quickly-in-older-version-of-dash-but-not-on-latest-version/31722/2
cc @nicolaskruchten as well