The "push" event should inherit from ExtendableEvent.

Source/modules/push_messaging/PushEvent.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/push_messaging/PushEvent.h"
 
 namespace blink {
 
 PushEventInit::PushEventInit()
 {
 }
 
 PushEvent::PushEvent()
 {
 }
 
-PushEvent::PushEvent(const AtomicString& type, const String& data)
-    : Event(type, /*canBubble=*/false, /*cancelable=*/false)
+PushEvent::PushEvent(const AtomicString& type, const String& data, WaitUntilObserver* observer)
+    : ExtendableEvent(type, ExtendableEventInit(), observer)
     , m_data(data)
 {
 }
 
 PushEvent::PushEvent(const AtomicString& type, const PushEventInit& initializer)
-    : Event(type, initializer)
+    : ExtendableEvent(type, initializer)
     , m_data(initializer.data)
 {
 }
 
 PushEvent::~PushEvent()
 {
 }
 
 const AtomicString& PushEvent::interfaceName() const
 {
     return EventNames::PushEvent;
 }
 
 } // namespace blink