Bug 1840776 - [devtools] Fix inspector crash on ::highlight. r=devtools-reviewers,jdescottes.

This prevent the rule view crashing when `dom.customHighlightAPI.enabled` is set
to true.

Differential Revision: https://phabricator.services.mozilla.com/D182327

devtools/server/actors/page-style.js

@@ -689,6 +689,9 @@ class PageStyleActor extends Actor {
       case "::first-line":
       case "::selection":
         return true;
+      // We don't want the method to throw, but we don't handle those yet (See Bug 1840872)
+      case "::highlight":
+        return false;
       case "::marker":
         return this._nodeIsListItem(node);
       case "::backdrop":