Use event init dictionaries in modules/{notifications,push_messaging,serviceworkers}

LayoutTests/http/tests/notifications/resources/serviceworker-notification-event.js

 importScripts('../../serviceworker/resources/worker-testharness.js');
 importScripts('/resources/testharness-helpers.js');
 
 test(function() {
     assert_true('NotificationEvent' in self);
 
     var event = new NotificationEvent('NotificationEvent');
     assert_equals(event.type, 'NotificationEvent');
     assert_own_property(event, 'notification');
+    assert_equals(event.cancelable, false);
+    assert_equals(event.bubbles, false);
+    assert_equals(event.notification, null);
     assert_inherits(event, 'waitUntil');
 
+    var notification = new Notification('foo');
+    var eventWithInit = new NotificationEvent('NotificationEvent',
+                                              { cancelable: true,
+                                                bubbles: true,
+                                                notification: notification,
+                                              });
+    assert_equals(eventWithInit.cancelable, true);
+    assert_equals(eventWithInit.bubbles, true);
+    assert_equals(eventWithInit.notification, notification);
+
 }, 'NotificationEvent is exposed, and has the expected interface.');
 
 test(function() {
     assert_own_property(self, 'onnotificationclick', 'The notificationclick event exists.');
     assert_own_property(self, 'onnotificationerror', 'The notificationerror event exists.');
 
 }, 'The notificationclick and notificationerror events exist on the global scope.');