BackgroundSync sync events need to be ExtendableEvents, blink side

Source/modules/serviceworkers/WaitUntilObserver.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "modules/serviceworkers/WaitUntilObserver.h"
 
 #include "bindings/core/v8/ScriptFunction.h"
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptValue.h"
@@ skipping 160 matching lines @@
         client->didHandleInstallEvent(m_eventID, result);
         break;
     case NotificationClick:
         client->didHandleNotificationClickEvent(m_eventID, result);
         m_consumeWindowInteractionTimer.stop();
         consumeWindowInteraction(nullptr);
         break;
     case Push:
         client->didHandlePushEvent(m_eventID, result);
         break;
+    case Sync:
+        client->didHandleSyncEvent(m_eventID, result);
+        break;
     }
     setContext(nullptr);
 }
 
 void WaitUntilObserver::consumeWindowInteraction(Timer<WaitUntilObserver>*)
 {
     if (!executionContext())
         return;
     executionContext()->consumeWindowInteraction();
 }
 
 DEFINE_TRACE(WaitUntilObserver)
 {
     ContextLifecycleObserver::trace(visitor);
 }
 
 } // namespace blink