Use safe bool conversion operators in fpdf_page/

core/fpdfapi/fpdf_page/include/cpdf_generalstate.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_GENERALSTATE_H_
 #define CORE_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_GENERALSTATE_H_
 
 #include "core/fxcrt/include/fx_basic.h"
 #include "core/fxcrt/include/fx_coordinates.h"
 #include "core/fxge/include/fx_dib.h"
 
 class CPDF_Object;
 class CPDF_TransferFunc;
 
 class CPDF_GeneralState {
  public:
   CPDF_GeneralState();
   CPDF_GeneralState(const CPDF_GeneralState& that);
   ~CPDF_GeneralState();
 
   void Emplace() { m_Ref.Emplace(); }
-  operator bool() const { return !!m_Ref; }
+  explicit operator bool() const { return !!m_Ref; }
 
   void SetRenderIntent(const CFX_ByteString& ri);
 
   int GetBlendType() const;
   void SetBlendType(int type);
 
   FX_FLOAT GetFillAlpha() const;
   void SetFillAlpha(FX_FLOAT alpha);
 
   FX_FLOAT GetStrokeAlpha() const;
@@ skipping 65 matching lines @@
     CPDF_Object* m_pUCR;
     CPDF_Object* m_pHT;
     FX_FLOAT m_Flatness;
     FX_FLOAT m_Smoothness;
   };
 
   CFX_CountRef<StateData> m_Ref;
 };
 
 #endif  // CORE_FPDFAPI_FPDF_PAGE_INCLUDE_CPDF_GENERALSTATE_H_