gistfile1.php

<?php

// Enable the plugin only when Jetpack and Sharedaddy are enabled

function shortlinks_for_sharing_buttons() {
	if (
		class_exists( 'Jetpack' ) && method_exists( 'Jetpack', 'get_active_modules' ) && in_array( 'sharedaddy', Jetpack::get_active_modules() )
		) {
		add_filter( 'sharing_permalink', 'get_shortlink_for_post' );
	}
}
add_action( 'plugins_loaded', 'shortlinks_for_sharing_buttons' );


// Grab the shortlink

function get_shortlink_for_post( $post ) {
	global $post;

	if ( !$post )
		return;

	$post_id = $post->ID;

	if( function_exists( 'get_yourls_shortlink' ) ) {
		if( get_yourls_shortlink() ) {
			return get_yourls_shortlink( $post_id );
		} else {
			return get_permalink( $post_id );
		}
	} else {
		return get_permalink( $post_id );
	}
}