[ServiceWorker] Don't allow registration of the ServiceWorker scope outside the script directory.

LayoutTests/http/tests/serviceworker/resources/test-helpers.js

 // Adapter for testharness.js-style tests with Service Workers
 
 function service_worker_unregister_and_register(test, url, scope) {
   if (!scope || scope.length == 0)
     return Promise.reject(new Error('tests must define a scope'));
 
   var options = { scope: scope };
   return service_worker_unregister(test, scope)
       .then(function() {
           return navigator.serviceWorker.register(url, options);
@@ skipping 181 matching lines @@
           break;
         case tests[i].NOTRUN:
           // Leave NOTRUN alone. It'll get marked as a NOTRUN when the test
           // terminates.
           break;
       }
     }
   };
 
   function service_worker_test(url, description) {
-    var scope = window.location.origin + '/service-worker-scope' +
+    var scope = new URL('./', new URL(url, window.location)) +
+      'resources/service-worker-scope' +
       window.location.pathname;
-
     var test = async_test(description);
     var registration;
     service_worker_unregister_and_register(test, url, scope)
       .then(function(r) {
           registration = r;
           return wait_for_update(test, registration);
         })
       .then(function(worker) { return fetch_tests_from_worker(worker); })
       .then(function() { return registration.unregister(); })
       .then(function() { test.done(); })
@@ skipping 42 matching lines @@
             channel.port1.onmessage = test.step_func(function() {
                 unload_iframe(frame).catch(function() {});
                 resolve();
               });
             frame.contentWindow.postMessage(
               {username: username, password: password},
               [channel.port2], origin);
           }));
     });
 }