Remove PlatformEvent it is no longer used.

third_party/WebKit/Source/core/input/ScrollManager.h

 // Copyright 2016 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 ScrollManager_h
 #define ScrollManager_h
 
 #include "core/CoreExport.h"
 #include "core/page/EventWithHitTestResults.h"
-#include "platform/PlatformEvent.h"
 #include "platform/geometry/LayoutSize.h"
 #include "platform/heap/Handle.h"
 #include "platform/heap/Visitor.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "public/platform/WebInputEventResult.h"
 #include "wtf/Allocator.h"
 #include <deque>
 
 namespace blink {
 
@@ skipping 120 matching lines @@
 
   Member<PaintLayerScrollableArea> m_resizeScrollableArea;
 
   LayoutSize
       m_offsetFromResizeCorner;  // In the coords of m_resizeScrollableArea.
 };
 
 }  // namespace blink
 
 #endif  // ScrollManager_h