ServiceWorker: Introduce ExtendableMessageEvent to replace MessageEvent

Source/modules/serviceworkers/WaitUntilObserver.cpp

Index: Source/modules/serviceworkers/WaitUntilObserver.cpp
diff --git a/Source/modules/serviceworkers/WaitUntilObserver.cpp b/Source/modules/serviceworkers/WaitUntilObserver.cpp
index 4c15898a06d36bf71dc8313462ed83cda4587d85..93e7a00d411adf72793eb264cdf7f9fa59b02a92 100644
--- a/Source/modules/serviceworkers/WaitUntilObserver.cpp
+++ b/Source/modules/serviceworkers/WaitUntilObserver.cpp
@@ -170,6 +170,9 @@ void WaitUntilObserver::decrementPendingActivity()
     case Install:
         client->didHandleInstallEvent(m_eventID, result);
         break;
+    case Message:
+        client->didHandleMessageEvent(m_eventID, result);
+        break;
     case NotificationClick:
         client->didHandleNotificationClickEvent(m_eventID, result);
         m_consumeWindowInteractionTimer.stop();