CPDF_Document::LoadPattern() and friends always have a valid matrix.

core/fpdfapi/fpdf_page/cpdf_tilingpattern.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_CPDF_TILINGPATTERN_H_
 #define CORE_FPDFAPI_FPDF_PAGE_CPDF_TILINGPATTERN_H_
 
 #include <memory>
 
 #include "core/fpdfapi/fpdf_page/cpdf_pattern.h"
 #include "core/fxcrt/include/fx_coordinates.h"
 #include "core/fxcrt/include/fx_system.h"
 
 class CPDF_Document;
 class CPDF_Form;
 class CPDF_Object;
 
 class CPDF_TilingPattern : public CPDF_Pattern {
  public:
   CPDF_TilingPattern(CPDF_Document* pDoc,
                      CPDF_Object* pPatternObj,
-                     const CFX_Matrix* parentMatrix);
+                     const CFX_Matrix& parentMatrix);
   ~CPDF_TilingPattern() override;
 
   CPDF_TilingPattern* AsTilingPattern() override { return this; }
   CPDF_ShadingPattern* AsShadingPattern() override { return nullptr; }
 
   FX_BOOL Load();
 
   bool colored() const { return m_bColored; }
   const CFX_FloatRect& bbox() const { return m_BBox; }
   FX_FLOAT x_step() const { return m_XStep; }
   FX_FLOAT y_step() const { return m_YStep; }
   CPDF_Form* form() const { return m_pForm.get(); }
 
  private:
   bool m_bColored;
   CFX_FloatRect m_BBox;
   FX_FLOAT m_XStep;
   FX_FLOAT m_YStep;
   std::unique_ptr<CPDF_Form> m_pForm;
 };
 
 #endif  // CORE_FPDFAPI_FPDF_PAGE_CPDF_TILINGPATTERN_H_