Ensure service worker script src is same as scope

[westonruter]

Fixes #231.

When testing the WPGlobus plugin I found that when accessing the Spanish-language version of the site at /es/ I was getting a service worker installed as:

navigator.serviceWorker.register(
	'https://example.com/es/?wp_service_worker=1',
	{ scope: '/'}
).then( reg => { /* ... */ });

Note the inconsistency in the scope of / and the script src having a base URL of /es/. This resulted in an error:

The path of the provided scope ('/') is not under the max scope allowed ('/es/'). Adjust the scope, move the Service Worker script, or use the Service-Worker-Allowed HTTP header to allow the scope.

The issue is that the WPGlobus plugin is apparently filtering the home_url differently based on the scheme being supplied to home_url(). So the quick fix is just to make sure that the home_url() used to obtain the script URL be made consistent with the URL used for the scope.

pwa-wp/wp-includes/service-workers.php

Line 142 in af49d9a

$scopes[ WP_Service_Workers::SCOPE_FRONT ] = home_url( '/', 'relative' ); // The home_url() here will account for subdirectory installs.

pwa-wp/wp-includes/service-workers.php

Lines 95 to 98 in af49d9a

	return add_query_arg(
	array( WP_Service_Workers::QUERY_VAR => $scope ),
	home_url( '/' )
	);

The issue is fixed merely by changing the latter from home_url( '/' ) to home_url( '/', 'relative ).

[westonruter]

Build for testing: pwa.zip (v0.4.0-alpha-e5fd349-20200329T184145Z)

[amedina]

LGTM!