Implement DragEvent and move MouseEvent.dataTransfer

Source/core/events/DragEvent.h

Index: Source/core/events/DragEvent.h
diff --git a/Source/core/events/DragEvent.h b/Source/core/events/DragEvent.h
new file mode 100644
index 0000000000000000000000000000000000000000..a2573c2ea2e89cff4909f8d5024e0efc450d08c7
--- /dev/null
+++ b/Source/core/events/DragEvent.h
@@ -0,0 +1,63 @@
+// Copyright 2015 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 DragEvent_h
+#define DragEvent_h
+
+#include "core/events/DragEventInit.h"
+#include "core/events/MouseEvent.h"
+
+namespace blink {
+
+class DataTransfer;
+
+class DragEvent final : public MouseEvent {
+    DEFINE_WRAPPERTYPEINFO();
+
+public:
+    static PassRefPtrWillBeRawPtr<DragEvent> create()
+    {
+        return adoptRefWillBeNoop(new DragEvent);
+    }
+
+    static PassRefPtrWillBeRawPtr<DragEvent> create(DataTransfer* dataTransfer)
+    {
+        return adoptRefWillBeNoop(new DragEvent(dataTransfer));
+    }
+
+    static PassRefPtrWillBeRawPtr<DragEvent> create(const AtomicString& type, const DragEventInit& initializer)
+    {
+        return adoptRefWillBeNoop(new DragEvent(type, initializer));
+    }
+
+    DataTransfer* dataTransfer() const override { return isDragEvent() ? m_dataTransfer.get() : 0; }
+
+    bool isDragEvent() const override;
+    bool isMouseEvent() const override;
+
+    DECLARE_VIRTUAL_TRACE();
+
+private:
+    DragEvent();
+    DragEvent(DataTransfer*);
+    DragEvent(const AtomicString& type, const DragEventInit&);
+
+    PersistentWillBeMember<DataTransfer> m_dataTransfer;
+};
+
+class DragEventDispatchMediator final : public EventDispatchMediator {
+public:
+    static PassRefPtrWillBeRawPtr<DragEventDispatchMediator> create(PassRefPtrWillBeRawPtr<DragEvent>);
+
+private:
+    explicit DragEventDispatchMediator(PassRefPtrWillBeRawPtr<DragEvent>);
+    DragEvent& event() const;
+    bool dispatchEvent(EventDispatcher&) const override;
+};
+
+DEFINE_EVENT_TYPE_CASTS(DragEvent);
+
+} // namespace blink
+
+#endif // DragEvent_h