Do not use a non-standard label attribute in shadow-dom.js

third_party/WebKit/LayoutTests/shadow-dom/resources/shadow-dom.js

 function removeWhiteSpaceOnlyTextNodes(node)
 {
     for (var i = 0; i < node.childNodes.length; i++) {
         var child = node.childNodes[i];
         if (child.nodeType === Node.TEXT_NODE && child.nodeValue.trim().length == 0) {
             node.removeChild(child);
             i--;
         } else if (child.nodeType === Node.ELEMENT_NODE || child.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
             removeWhiteSpaceOnlyTextNodes(child);
         }
@@ skipping 49 matching lines @@
         else if (isShadowHost(node))
             node = node.shadowRoot.getElementById(ids[i]);
         else
             return null;
     }
     return node;
 }
 
 function createTestTree(node) {
 
-  let labels = {};
+  let ids = {};
 
   function attachShadowFromTemplate(template) {
     let parent = template.parentNode;
     parent.removeChild(template);
     let shadowRoot = parent.attachShadow({mode: template.getAttribute('data-mode')});
-    let label = template.getAttribute('label');
-    if (label) {
-      shadowRoot.id = label;
-      labels[label] = shadowRoot;
+    let id = template.id;
+    if (id) {
+      shadowRoot.id = id;
+      ids[id] = shadowRoot;
     }
     shadowRoot.appendChild(document.importNode(template.content, true));
     return shadowRoot;
   }
 
   function walk(root) {
-    if (root.getAttribute && root.getAttribute('label')) {
-      labels[root.getAttribute('label')] = root;
+    if (root.id) {
+      ids[root.id] = root;
     }
-    for (let e of Array.from(root.querySelectorAll('[label]'))) {
-      labels[e.getAttribute('label')] = e;
+    for (let e of Array.from(root.querySelectorAll('[id]'))) {
+      ids[e.id] = e;
     }
     for (let e of Array.from(root.querySelectorAll('template'))) {
       walk(attachShadowFromTemplate(e));
     }
   }
 
   walk(node.cloneNode(true));
-  return labels;
+  return ids;
 }
 
 function dispatchEventWithLog(nodes, target, event) {
 
   function labelFor(e) {
-    if (e.getAttribute && e.getAttribute('label')) {
-      return e.getAttribute('label');
-    }
     return e.id || e.tagName;
   }
 
   let log = [];
   let attachedNodes = [];
   for (let label in nodes) {
     let startingNode = nodes[label];
     for (let node = startingNode; node; node = node.parentNode) {
       if (attachedNodes.indexOf(node) >= 0)
         continue;
-      let label = labelFor(node);
-      if (!label)
+      let id = node.id;
+      if (!id)
         continue;
       attachedNodes.push(node);
       node.addEventListener(event.type, (e) => {
-        log.push([label,
+        log.push([id,
                   event.relatedTarget ? labelFor(event.relatedTarget) : null,
                   event.composedPath().map((n) => {
                     return labelFor(n);
                   })]);
       });
     }
   }
   target.dispatchEvent(event);
   return log;
 }
 
 // This function assumes that testharness.js is available.
 function assert_event_path_equals(actual, expected) {
   assert_equals(actual.length, expected.length);
   for (let i = 0; i < actual.length; ++i) {
     assert_equals(actual[i][0], expected[i][0], 'currentTarget at ' + i + ' should be same');
     assert_equals(actual[i][1], expected[i][1], 'relatedTarget at ' + i + ' should be same');
     assert_array_equals(actual[i][2], expected[i][2], 'composedPath at ' + i + ' should be same');
   }
 }