Use event init dictionaries in modules/{notifications,push_messaging,serviceworkers}

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, PushMessageData* data, WaitUntilObserver* observer)
     : ExtendableEvent(type, ExtendableEventInit(), observer)
     , m_data(data)
 {
 }
 
 PushEvent::PushEvent(const AtomicString& type, const PushEventInit& initializer)
     : ExtendableEvent(type, initializer)
-    , m_data(initializer.data)
 {
+    if (initializer.hasData())
+        m_data = initializer.data();
 }
 
 PushEvent::~PushEvent()
 {
 }
 
 const AtomicString& PushEvent::interfaceName() const
 {
     return EventNames::PushEvent;
 }
 
 PushMessageData* PushEvent::data()
 {
     if (!m_data)
         m_data = PushMessageData::create();
 
     return m_data.get();
 }
 
 void PushEvent::trace(Visitor* visitor)
 {
     visitor->trace(m_data);
     ExtendableEvent::trace(visitor);
 }
 
 } // namespace blink