[flexiglass] Adds TODO for removing WindowRootView#isRoot

     * Please see the class-level documentation to understand why this is possible.

     */

    private fun isRoot(): Boolean {

        // TODO(b/283300105): remove this check once there's only one subclass of WindowRootView.

        return parent.let { it !is View || it.id == android.R.id.content }

    }

}