Add font size button into Wordpress TinyMCE

functions.php

function wp_editor_fontsize_filter( $buttons ) {
    array_shift( $buttons );
    array_unshift( $buttons, 'fontsizeselect');
    array_unshift( $buttons, 'formatselect');
    return $buttons;
}
add_filter('mce_buttons_2', 'wp_editor_fontsize_filter');

// Customize mce editor font sizes

function wp_mce_text_sizes( $initArray ){
    $initArray['theme_advanced_font_sizes'] = "9px 10px 12px 13px 14px 16px 18px 21px 24px 28px 32px 36px";
    $initArray['fontsize_formats'] = "9px 10px 12px 13px 14px 16px 18px 21px 24px 28px 32px 36px";
    return $initArray;
}
add_filter( 'tiny_mce_before_init', 'wp_mce_text_sizes' );