Add some layout tests for Notification.data on persistent notifications

LayoutTests/http/tests/notifications/serviceworker-notificationclick-event-reflection.html

Index: LayoutTests/http/tests/notifications/serviceworker-notificationclick-event-reflection.html
diff --git a/LayoutTests/http/tests/notifications/serviceworker-notificationclick-event-reflection.html b/LayoutTests/http/tests/notifications/serviceworker-notificationclick-event-reflection.html
index 7f5fb86af852a90fea877b8a81db6442d05331bc..23d34c282dbd2d02682e2ff1b16096bb2234f97b 100644
--- a/LayoutTests/http/tests/notifications/serviceworker-notificationclick-event-reflection.html
+++ b/LayoutTests/http/tests/notifications/serviceworker-notificationclick-event-reflection.html
@@ -26,7 +26,13 @@
               // FIXME: Relative URLs for the icon attribute currently get reflected as
               // an absolute URL, which should probably be the given relative URL.
               icon: 'https://example/icon.png',
-              silent: true
+              silent: true,
+              data: [
+                  { property: 'foobar',
+                    string: '\uDFFF\u0000\uDBFF',
+                    scalar: true },
+                  12.15
+              ]
           };
 
           testRunner.grantWebNotificationPermission(location.origin, true);
@@ -59,9 +65,14 @@
                   assert_equals(event.data.command, 'click', 'The notification was expected to be clicked.');
 
                   Object.keys(options).forEach(function(key) {
+                      if (key == 'data')
+                          return;  // Check "data" separately to avoid stringifying it.
+
                       assert_equals(event.data.notification[key], options[key], 'The ' + key + ' field must be the same.');
                   });
 
+                  assert_object_equals(event.data.notification.data, options.data, 'The data field must be the same.');
+
                   test.done();
               });
           }).catch(unreached_rejection(test));