ServiceWorker: Introduce ServiceWorkerMessageEvent to replace MessageEvent (3/3).

LayoutTests/http/tests/serviceworker/interfaces.html

Index: LayoutTests/http/tests/serviceworker/interfaces.html
diff --git a/LayoutTests/http/tests/serviceworker/interfaces.html b/LayoutTests/http/tests/serviceworker/interfaces.html
index 22aecefd4356a8e5611b726b095ab535e1a677b1..8fc2a43433108e90ee1bdf63c3d464d3dcc2e755 100644
--- a/LayoutTests/http/tests/serviceworker/interfaces.html
+++ b/LayoutTests/http/tests/serviceworker/interfaces.html
@@ -13,7 +13,8 @@ test(function() {
       {
         register: 'function',
         getRegistration: 'function',
-        oncontrollerchange: EVENT_HANDLER
+        oncontrollerchange: EVENT_HANDLER,
+        onmessage: EVENT_HANDLER
       });
   }, 'Interfaces and attributes of ServiceWorkerContainer');