fn prompt_user_for_credentials(
embedder_proxy: &Mutex<EmbedderProxy>,
top_level_browsing_context_id: Option<TopLevelBrowsingContextId>,
) -> Option<PromptCredentialsInput>
fn prompt_user_for_credentials(
embedder_proxy: &Mutex<EmbedderProxy>,
top_level_browsing_context_id: Option<TopLevelBrowsingContextId>,
) -> Option<PromptCredentialsInput>