Fact: Recalculating unique name depends on state of other frames (and therefore calculating unique name for the same assigned name can give different result, depending on the sate of other frames).

Requirement: Setting window.name to the same value should not change unique name.

Currently this requirement is not met - with a carefully crafted layout test we can hit the DCHECK below:

  content/browser/frame_host/frame_tree_node.cc:

    void FrameTreeNode::SetFrameName(const std::string& name,
                                     const std::string& unique_name) {
      if (name == replication_state_.name) {
        // |unique_name| shouldn't change unless |name| changes.
        DCHECK_EQ(unique_name, replication_state_.unique_name);
        return;
      }