relax requirement for re-calc

- recalc when gd.calcdata doesn't match with fullData (not gd.data)

Author: etpinard

src/plot_api/plot_api.js

@@ -140,7 +140,7 @@ Plotly.plot = function(gd, data, layout, config) {
 
     // generate calcdata, if we need to
     // to force redoing calcdata, just delete it before calling Plotly.plot
-    var recalc = !gd.calcdata || gd.calcdata.length !== (gd.data || []).length;
+    var recalc = !gd.calcdata || gd.calcdata.length !== (gd._fullData || []).length;
     if(recalc) Plots.doCalcdata(gd);
 
     // in case it has changed, attach fullData traces to calcdata