fix svgTextUtils for FF: use child element instead of SVG to getSize()
fix svgTextUtils for FF: use child element instead of SVG to getSize()

plotly/plotly.js,aburato/plotly.js,plotly/plotly.js,etpinard/plotly.js,aburato/plotly.js,etpinard/plotly.js,plotly/plotly.js,plotly/plotly.js,etpinard/plotly.js