bluetooth: {start,stop}Notifications() return the characteristic

third_party/WebKit/LayoutTests/bluetooth/notifications/stop-after-start-succeeds.html

Index: third_party/WebKit/LayoutTests/bluetooth/notifications/stop-after-start-succeeds.html
diff --git a/third_party/WebKit/LayoutTests/bluetooth/notifications/start-stop-start-stop.html b/third_party/WebKit/LayoutTests/bluetooth/notifications/stop-after-start-succeeds.html
similarity index 58%
copy from third_party/WebKit/LayoutTests/bluetooth/notifications/start-stop-start-stop.html
copy to third_party/WebKit/LayoutTests/bluetooth/notifications/stop-after-start-succeeds.html
index 1e65acbfe0d335b524c6e716900e8a04bb169369..ca0832bf0ade95f15fa0efcbd4fd822948930790 100644
--- a/third_party/WebKit/LayoutTests/bluetooth/notifications/start-stop-start-stop.html
+++ b/third_party/WebKit/LayoutTests/bluetooth/notifications/stop-after-start-succeeds.html
@@ -13,11 +13,17 @@ promise_test(() => {
     .then(service => service.getCharacteristic('heart_rate_measurement'))
     .then(characteristic => {
       return characteristic.startNotifications()
-        .then(() => characteristic.stopNotifications())
-        .then(() => characteristic.startNotifications())
-        .then(() => characteristic.stopNotifications());
-    });
+        .then(start_characteristic => {
+            assert_equals(start_characteristic, characteristic,
+                'Start characteristic should the same as characteristic.');
+            return characteristic.stopNotifications()
+              .then(stop_characteristic => {
+                assert_equals(stop_characteristic, start_characteristic,
+                    'Stop characteristic should the same as start characteristic.');
+              });
+         });
+     });
   // TODO(ortuno): Assert that notifications are not active.
   // http://crbug.com/600762
-}, 'Start -> stop -> start -> stop.');
+}, 'Single stop after start notifications succeeds.');
 </script>