Fix a regression in discovery of shared vdom nodes

Author: gre

src/data/fill.js

@@ -3,7 +3,7 @@
 function fill (dataTree) {
   function fillRec (node) {
     // we compute all the descendants vdom under the current node
-    let descendantsVDOM = [], descendantsVDOMData = [];
+    let descendantsVDOM = [ node.vdom ], descendantsVDOMData = [ node.data ];
     const newChildren = node.data.children.map(node => {
       const res = fillRec(node);
       if (descendantsVDOM.indexOf(res.vdom) === -1) {