Update PushEvent and PushMessageData to match the spec.

Source/modules/push_messaging/PushEvent.h

 // 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.
 
 #ifndef PushEvent_h
 #define PushEvent_h
 
 #include "modules/EventModules.h"
 #include "modules/ModulesExport.h"
-#include "modules/push_messaging/PushEventInit.h"
 #include "modules/push_messaging/PushMessageData.h"
 #include "modules/serviceworkers/ExtendableEvent.h"
 #include "platform/heap/Handle.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
+class PushEventInit;
+
 class MODULES_EXPORT PushEvent final : public ExtendableEvent {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static PassRefPtrWillBeRawPtr<PushEvent> create()
     {
         return adoptRefWillBeNoop(new PushEvent);
     }
     static PassRefPtrWillBeRawPtr<PushEvent> create(const AtomicString& type, PushMessageData* data, WaitUntilObserver* observer)
     {
         return adoptRefWillBeNoop(new PushEvent(type, data, observer));
@@ skipping 15 matching lines @@
     PushEvent();
     PushEvent(const AtomicString& type, PushMessageData*, WaitUntilObserver*);
     PushEvent(const AtomicString& type, const PushEventInit&);
 
     PersistentWillBeMember<PushMessageData> m_data;
 };
 
 } // namespace blink
 
 #endif // PushEvent_h