Enumerate the return value of dispatchEvent so it is clear.

third_party/WebKit/Source/core/events/DragEvent.h

 // 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/CoreExport.h"
 #include "core/events/DragEventInit.h"
 #include "core/events/MouseEvent.h"
@@ skipping 54 matching lines @@
     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;
+    DispatchEventResult dispatchEvent(EventDispatcher&) const override;
 };
 
 DEFINE_EVENT_TYPE_CASTS(DragEvent);
 
 } // namespace blink
 
 #endif // DragEvent_h