DevTools: Replace visibleChildrenCount with hasVisibleChildren in ElementsTreeOutline.

LayoutTests/http/tests/inspector/elements-test.js

 function getInspectorHighlightJSON(nodeId, opt_frameId)
 {
     var doc = document;
     if (opt_frameId)
         doc = document.getElementById(opt_frameId).contentDocument;
     return window.internals.inspectorHighlightJSON(doc.getElementById(nodeId));
 }
 
 var initialize_ElementTest = function() {
 
 InspectorTest.preloadPanel("elements");
 
 InspectorTest.findNode = function(matchFunction, callback)
 {
     callback = InspectorTest.safeWrap(callback);
     var result = null;
     var pendingRequests = 0;
     function processChildren(node)
     {
         try {
             if (result)
                 return;
 
-            var children = (node.children() || []).concat(node.shadowRoots()).concat(Object.values(node.pseudoElements() || {}));
+            var pseudoElementsMap = node.pseudoElements();
+            var pseudoElements = pseudoElementsMap ? pseudoElementsMap.valuesArray() : [];
+            var children = (node.children() || []).concat(node.shadowRoots()).concat(pseudoElements);
             if (node.templateContent())
                 children.push(node.templateContent());
             else if (node.importedDocument())
                 children.push(node.importedDocument());
 
             for (var i = 0; i < children.length; ++i) {
                 var childNode = children[i];
                 if (matchFunction(childNode)) {
                     result = childNode;
                     callback(result);
@@ skipping 792 matching lines @@
     function innerCallback(result)
     {
         InspectorTest.addResult(nodeId + ": " + result.description);
         callback();
     }
     opt_frameId = opt_frameId || "";
     InspectorTest.evaluateInPage("getInspectorHighlightJSON(\"" + nodeId + "\", \"" + opt_frameId + "\")", innerCallback);
 }
 
 };