test: hiding and showing back a legend
test: hiding and showing back a legend

* Tested that event listeners in a legend work after hiding and
  showing back the legend.

asolagmbh/plotly.js,aburato/plotly.js,iongroup/plotly.js,iongroup/plotly.js,plotly/plotly.js,etpinard/plotly.js,asolagmbh/plotly.js,plotly/plotly.js,plotly/plotly.js,etpinard/plotly.js,plotly/plotly.js,aburato/plotly.js,etpinard/plotly.js,iongroup/plotly.js,asolagmbh/plotly.js