DevTools: migrate inspector-protocol/dom tests to a new test runner

third_party/WebKit/LayoutTests/inspector-protocol/resources/node-tracker.js

+(class NodeTracker {
+  constructor(dp) {
+    this._nodes = new Map();
+    dp.DOM.onSetChildNodes(message => message.params.nodes.forEach(node => this._addNode(node)));
+  }
+
+  addDocumentNode(documentNode) {
+    this._addNode(documentNode);
+  }
+
+  _addNode(node) {
+    this._nodes.set(node.nodeId, node);
+    if (node.children)
+      node.children.forEach(node => this._addNode(node));
+  }
+
+  nodeForId(nodeId) {
+    return this._nodes.get(nodeId) || null;
+  }
+
+  nodes() {
+    return Array.from(this._nodes.values());
+  }
+
+  nodeIds() {
+    return Array.from(this._nodes.keys());
+  }
+})