Change default "+ New" content post type to page in WordPress administration menu bar

functions.admin_bar_menu.new_content.php

<?php

/**
 * code to be placed in theme functions.php
 * add_filter priority of 70 or greater.
 */
if ( ! function_exists( 'mytheme_admin_bar_menu' ) ) {
	function mytheme_admin_bar_menu( $wp_admin_bar ) {

		$new_content = (object) $wp_admin_bar->get_node( 'new-content' );
		if ( ! empty( $new_content->href ) ) {
			$new_content->href = admin_url( 'post-new.php?post_type=page' );
			$wp_admin_bar->add_node( $new_content );
		}

	}

	add_filter( 'admin_bar_menu', 'mytheme_admin_bar_menu', 70 );
}