Use safe bool conversion operators in fpdf_page/

core/fpdfapi/fpdf_page/include/cpdf_path.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 CORE_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_PATH_H_
 #define CORE_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_PATH_H_
 
 #include "core/fxcrt/include/cfx_count_ref.h"
 #include "core/fxcrt/include/fx_system.h"
 #include "core/fxge/include/cfx_fxgedevice.h"
 #include "core/fxge/include/cfx_pathdata.h"
 #include "core/fxge/include/cfx_renderdevice.h"
 
 class CPDF_Path {
  public:
   CPDF_Path();
   CPDF_Path(const CPDF_Path& that);
   ~CPDF_Path();
 
   void Emplace() { m_Ref.Emplace(); }
-  operator bool() const { return !!m_Ref; }
+  explicit operator bool() const { return !!m_Ref; }
 
   int GetPointCount() const;
   void SetPointCount(int count);
   const FX_PATHPOINT* GetPoints() const;
   FX_PATHPOINT* GetMutablePoints();
 
   int GetFlag(int index) const;
   FX_FLOAT GetPointX(int index) const;
   FX_FLOAT GetPointY(int index) const;
   CFX_FloatRect GetBoundingBox() const;
   CFX_FloatRect GetBoundingBox(FX_FLOAT line_width, FX_FLOAT miter_limit) const;
 
   FX_BOOL IsRect() const;
   void Transform(const CFX_Matrix* pMatrix);
 
   void Append(const CPDF_Path& other, const CFX_Matrix* pMatrix);
   void Append(const CFX_PathData* pData, const CFX_Matrix* pMatrix);
   void AppendRect(FX_FLOAT left, FX_FLOAT bottom, FX_FLOAT right, FX_FLOAT top);
 
   // TODO(tsepez): Remove when all access thru this class.
   const CFX_PathData* GetObject() const { return m_Ref.GetObject(); }
 
  private:
   CFX_CountRef<CFX_PathData> m_Ref;
 };
 
 #endif  // CORE_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_PATH_H_