How do I use mutationobserver instead of mutation events?

I am trying to create my first streamgraph with D3.js. I am starting with a working example which incorporates a tooltip from code posted on-line, http://bl.ocks.org/WillTurman/4631136:

When I copy the index.html and data.csv files to my PC (Windows 7), I am able to see the streamgraph in a browser (Firefox). However, I get a JS warning, "Use of Mutation Events is deprecated. Use MutationObserver instead."

What lines of code correspond to the Mutation Event? And how should I edit them to use a MutationObserver instead?

I am new to D3 and javascript. Although I found some discussion of mutation events and MutationObservers on-line, I didn't see any examples that were basic enough for me to understand and apply to my situation. I would appreciate any tips.

This is something that will need to be changed in the D3 source. As a user (and certainly as a beginner), you don't need to worry about this -- the warning is only relevant to the developers. Feel free to open an issue about this.