ght now.
      const browsingContext = node.ownerGlobal?.browsingContext;

      // For not yet cached nodes generate a unique id without curly braces.
      nodeId = lazy.generateUUID();

      const details = {
        browserId: browsingContext?.browserId,
        browsingContextGroupId: browsingContext?.group.id,
        browsingContextId: browsingContext?.id,
        isTopBrowsingContext: browsingContext?.parent === null,
        nodeWeakRef: Cu.getWeakReference(node),
      };

      this.#nodeIdMap.set(node, nodeId);
      this.#seenNodesMap.set(nodeId, details);

      // Also add the information for the node id and its correlated browsing
      // context to allow the parent process to update the seen nodes.
      if (!seenNodeIds.has(browsingContext)) {
        seenNodeIds.set(browsingContext, []);
      }
      seenNodeIds.get(browsingContext).push(nodeId);
    }

    return nodeId;
  }

  /**
   * Clear known DOM nodes.
   *
   * @param {object=} options
   * @param {boolean=} options.all
   *     Clear all references from any browsing context. Defaults to false.
   * @param {BrowsingContext=} options.browsingContext
   *     Clear all references living in that browsing context.
   */
  clear(options = {}) {
    const { all = false, browsingContext } = options;

    if (all) {
      this.#nodeIdMap = new WeakMap();
      this.#seenNodesMap.clear();
      return;
    }

    if (browsingContext) {
      for (const [nodeId, identifier] of this.#seenNodesMap.entries()) {
        const { browsingContextId, nodeWeakRef } = identifier;
        const node = nodeWeakRef.get();

        if (browsingContextId === browsingContext.id) {
          this.#nodeIdMap.delete(node);
          this.#seenNodesMap.delete(nodeId);
        }
      }

      return;
    }

    throw new Error(`Requires "browsingContext" or "all" to be set.`);
  }

  /**
   * Get a DOM node by its unique reference.
   *
   * @param {BrowsingContext} browsingContext
   *     The browsing context the node should be part of.
   * @param {string} nodeId
   *     The unique node reference of the DOM node.
   *
   * @returns {Node|null}
   *     The DOM node that the unique identifier was generated for or
   *     `null` if the node does not exist anymore.
   */
  getNode(browsingContext, nodeId) {
    const nodeDetails = this.getReferenceDetails(nodeId);

    // Check that the node reference is known, and is associated with a
    // browsing context that shares the same browsing context group.
    if (
      nodeDetails === null ||
      nodeDetails.browsingContextGroupId !== browsingContext.group.id
    ) {
      return null;
    }

    if (nodeDetails.nodeWeakRef) {
      return nodeDetails.nodeWeakRef.get();
    }

    return null;
  }

  /**
   * Get detailed information for the node reference.
   *
   * @param {string} nodeId
   *
   * @returns {NodeReferenceDetails}
   *     Node details like: browsingContextId
   */
  getReferenceDetails(nodeId) {
    const details = this.#seenNodesMap.get(nodeId);

    return details !== undefined ? details : null;
  }
}
PK