Tidy up representation of ScrollState::m_data.

third_party/WebKit/Source/core/page/scrolling/ScrollState.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 ScrollState_h
 #define ScrollState_h
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/CoreExport.h"
-#include "core/dom/Element.h"
 #include "core/page/scrolling/ScrollStateInit.h"
 #include "platform/scroll/ScrollStateData.h"
+#include "wtf/Forward.h"
 #include <deque>
 
 namespace blink {
 
+class Element;
+
 class CORE_EXPORT ScrollState final : public GarbageCollectedFinalized<ScrollState>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 
 public:
     static ScrollState* create(ScrollStateInit);
     static ScrollState* create(PassOwnPtr<ScrollStateData>);
 
     ~ScrollState()
     {
     }
@@ skipping 55 matching lines @@
     {
         return !m_data->delta_x && !m_data->delta_y && !m_data->is_ending && !m_data->is_beginning;
     }
 
     ScrollStateData* data() const { return m_data.get(); }
 
     DEFINE_INLINE_TRACE() {}
 
 private:
     ScrollState();
-    ScrollState(PassOwnPtr<ScrollStateData>);
-    PassOwnPtr<ScrollStateData> m_data;
+    explicit ScrollState(PassOwnPtr<ScrollStateData>);
+
+    OwnPtr<ScrollStateData> m_data;
     std::deque<int> m_scrollChain;
 };
 
 } // namespace blink
 
 #endif // ScrollState_h