merge top-paper <defs> into main svg on to-svg step

Author: etpinard

src/snapshot/tosvg.js

@@ -89,10 +89,21 @@ module.exports = function toSVG(gd, format) {
     // assumes everything in toppaper is a group, and if it's empty (like hoverlayer)
     // we can ignore it
     if(fullLayout._toppaper) {
-        var topGroups = fullLayout._toppaper.node().childNodes,
-            topGroup;
+        var topDefs = fullLayout._topdefs.node().childNodes;
+
+        for(i = 0; i < topDefs.length; i++) {
+            var topDef = topDefs[i];
+
+            fullLayout._defs.node().appendChild(topDef);
+        }
+
+        fullLayout._topdefs.remove();
+
+        var topGroups = fullLayout._toppaper.node().childNodes;
+
         for(i = 0; i < topGroups.length; i++) {
-            topGroup = topGroups[i];
+            var topGroup = topGroups[i];
+
             if(topGroup.childNodes.length) svg.node().appendChild(topGroup);
         }
     }