Clean up singleton implementation

xfa/fwl/theme/cfwl_arrowdata.h

+// Copyright 2016 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#ifndef XFA_FWL_THEME_CFWL_ARROWDATA_H_
+#define XFA_FWL_THEME_CFWL_ARROWDATA_H_
+
+#include <memory>
+
+#include "core/fxcrt/include/fx_system.h"
+#include "core/fxge/include/fx_dib.h"
+
+class CFWL_ArrowData {
+ public:
+  struct CColorData {
+    FX_ARGB clrBorder[4];
+    FX_ARGB clrStart[4];
+    FX_ARGB clrEnd[4];
+    FX_ARGB clrSign[4];
+  };
+
+  static CFWL_ArrowData* GetInstance();
+  static FX_BOOL HasInstance();
+  static void DestroyInstance();
+  void SetColorData(uint32_t dwID);
+
+  std::unique_ptr<CColorData> m_pColorData;
+
+ private:
+  CFWL_ArrowData();
+  ~CFWL_ArrowData();
+};
+
+#endif  // XFA_FWL_THEME_CFWL_ARROWDATA_H_