Add support for RelatedEvent.

Source/core/events/RelatedEvent.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 RelatedEvent_h
+#define RelatedEvent_h
+
+#include "core/events/Event.h"
+
+namespace blink {
+
+struct RelatedEventInit : public EventInit {
+    RelatedEventInit();
+    RefPtrWillBeMember<EventTarget> relatedTarget;
+};
+
+class RelatedEvent FINAL : public Event {
+public:
+    static PassRefPtrWillBeRawPtr<RelatedEvent> create();

[tkent, 2014/08/06 12:56:02]

Is this necessary?

[pals, 2014/08/06 13:05:13]

This is reffered by this
https://code.google.com/p/chromium/codesearch#chromium/src/out/Debug/gen/blin...

+    static PassRefPtrWillBeRawPtr<RelatedEvent> create(const AtomicString& type, bool canBubble, bool cancelable, EventTarget* relatedTarget);
+    static PassRefPtrWillBeRawPtr<RelatedEvent> create(const AtomicString& eventType, const RelatedEventInit&);
+
+    virtual ~RelatedEvent();
+
+    EventTarget* relatedTarget() const { return m_relatedTarget.get(); }
+    void setRelatedTarget(PassRefPtrWillBeRawPtr<EventTarget> relatedTarget) { m_relatedTarget = relatedTarget; }

[tkent, 2014/08/06 12:56:02]

EventTarget* is enough for the argument.  We don't need to use PassRefPtr, and
it's consistent with a factory method.

[pals, 2014/08/06 13:05:13]

Done.

[tkent, 2014/08/06 23:19:34]

I think this function won't be used.  Let's remove this in a following patch if
it is unnecessary.

+
+
+    virtual const AtomicString& interfaceName() const OVERRIDE { return EventNames::RelatedEvent; }
+    virtual bool isRelatedEvent() const OVERRIDE { return true; }
+
+    virtual void trace(Visitor*) OVERRIDE;
+
+private:
+    RelatedEvent();
+    RelatedEvent(const AtomicString& type, bool canBubble, bool cancelable, EventTarget*);
+    RelatedEvent(const AtomicString& type, const RelatedEventInit&);
+
+    RefPtrWillBeMember<EventTarget> m_relatedTarget;
+};
+
+DEFINE_EVENT_TYPE_CASTS(RelatedEvent);
+
+} // namespace blink
+
+#endif // RelatedEvent_h