WordPress at a glance
filter is not described

icon_dir_uri filter-hook . WP 2.0.0

Filters the icon directory URI.

Usage

add_filter( 'icon_dir_uri', 'filter_function_name_5787' );
function filter_function_name_5787( $uri ){
	// filter...

	return $uri;
}
$uri(string)
Icon directory URI.

Where the hook is called

wp_mime_type_icon()
wp-includes/post.php 5590
$icon_dir_uri = apply_filters( 'icon_dir_uri', includes_url( 'images/media' ) );

Where the hook is used (in WP core)

Does not used.