generalize _autoBinFinished for histogram2d

- this fixes some shared histogram2d (via bingroup) edge cases
- this fixes a performance regression from #3845

src/plots/plots.js

@@ -2961,7 +2961,10 @@ function sortAxisCategoriesByValue(axList, gd) {
                 if(fullTrace.visible !== true) continue;
 
                 var type = fullTrace.type;
-                if(Registry.traceIs(fullTrace, 'histogram')) delete fullTrace._autoBinFinished;
+                if(Registry.traceIs(fullTrace, 'histogram')) {
+                    delete fullTrace._xautoBinFinished;
+                    delete fullTrace._yautoBinFinished;
+                }
 
                 var cd = gd.calcdata[traceIndex];
                 for(k = 0; k < cd.length; k++) {

src/traces/histogram/calc.js

@@ -232,8 +232,8 @@ function calcAllAutoBins(gd, trace, pa, mainData, _overlayEdgeCase) {
 
     // all but the first trace in this group has already been marked finished
     // clear this flag, so next time we run calc we will run autobin again
-    if(trace._autoBinFinished) {
-        delete trace._autoBinFinished;
+    if(trace['_' + mainData + 'autoBinFinished']) {
+        delete trace['_' + mainData + 'autoBinFinished'];
     } else {
         traces = binOpts.traces;
         var allPos = [];
@@ -253,14 +253,14 @@ function calcAllAutoBins(gd, trace, pa, mainData, _overlayEdgeCase) {
                 pos0 = tracei['_' + mainDatai + 'pos0'] = pa.makeCalcdata(tracei, mainDatai);
 
                 allPos = Lib.concat(allPos, pos0);
-                delete tracei._autoBinFinished;
+                delete tracei['_' + mainData + 'autoBinFinished'];
 
                 if(trace.visible === true) {
                     if(isFirstVisible) {
                         isFirstVisible = false;
                     } else {
                         delete tracei._autoBin;
-                        tracei._autoBinFinished = 1;
+                        tracei['_' + mainData + 'autoBinFinished'] = 1;
                     }
                     if(Registry.traceIs(tracei, '2dMap')) {
                         has2dMap = true;
@@ -421,7 +421,7 @@ function handleSingleValueOverlays(gd, trace, pa, mainData, binAttr) {
 
             // so we can use this result when we get to tracei in the normal
             // course of events, mark it as done and put _pos0 back
-            tracei._autoBinFinished = 1;
+            tracei['_' + mainData + 'autoBinFinished'] = 1;
             tracei['_' + mainData + 'pos0'] = resulti[1];
 
             if(isSingleValued) {

src/traces/histogram/cross_trace_defaults.js

@@ -106,7 +106,8 @@ module.exports = function crossTraceDefaults(fullData, fullLayout) {
 
             // TODO: this shouldn't be relinked as it's only used within calc
             // https://github.com/plotly/plotly.js/issues/749
-            delete traceOut._autoBinFinished;
+            delete traceOut._xautoBinFinished;
+            delete traceOut._yautoBinFinished;
 
             // N.B. need to coerce *alignmentgroup* before *bingroup*, as traces
             // in same alignmentgroup "have to match"