[DevTools] Accessibility pane: Sync highlight between a11y pane and DOM pane

third_party/WebKit/Source/devtools/front_end/accessibility/AXTreePane.js

Index: third_party/WebKit/Source/devtools/front_end/accessibility/AXTreePane.js
diff --git a/third_party/WebKit/Source/devtools/front_end/accessibility/AXTreePane.js b/third_party/WebKit/Source/devtools/front_end/accessibility/AXTreePane.js
index c7a24626bac1d6375410c4f6343b01737fc3895b..88ed1ee7e86b4dfc38922fcb3f44c90e16fea6b1 100644
--- a/third_party/WebKit/Source/devtools/front_end/accessibility/AXTreePane.js
+++ b/third_party/WebKit/Source/devtools/front_end/accessibility/AXTreePane.js
@@ -180,8 +180,32 @@ Accessibility.AXNodeTreeElement = class extends UI.TreeElement {
     this._treePane = treePane;
 
     this.selectable = true;
+    this.paddingSize = 12;
+    this._hovered = false;
 
     this._inspectNodeButton = new Accessibility.InspectNodeButton(axNode, treePane);
+    this.listItemElement.addEventListener('mousemove', this._onmousemove.bind(this), false);
+    this.listItemElement.addEventListener('mouseleave', this._onmouseleave.bind(this), false);
+  }
+
+  /**
+   * @param {boolean} x
+   */
+  setHovered(x) {
+    if (this._hovered === x)
+      return;
+    this._hovered = x;
+    this.listItemElement.classList.toggle('hovered', x);
+    if (this._hovered)
+      this._axNode.highlightDOMNode();
+  }
+
+  _onmousemove(event) {
+    this.setHovered(true);
+  }
+
+  _onmouseleave(event) {
+    this.setHovered(false);
   }
 
   /**