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

core/fpdfapi/fpdf_parser/include/cpdf_document.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_PARSER_INCLUDE_CPDF_DOCUMENT_H_
 #define CORE_FPDFAPI_FPDF_PARSER_INCLUDE_CPDF_DOCUMENT_H_
 
 #include <memory>
@@ skipping 52 matching lines @@
 
   FX_BOOL IsFormStream(uint32_t objnum, FX_BOOL& bForm) const;
 
   // |pFontDict| must not be null.
   CPDF_Font* LoadFont(CPDF_Dictionary* pFontDict);
   CPDF_ColorSpace* LoadColorSpace(CPDF_Object* pCSObj,
                                   CPDF_Dictionary* pResources = NULL);
 
   CPDF_Pattern* LoadPattern(CPDF_Object* pObj,
                             FX_BOOL bShading,
-                            const CFX_Matrix* matrix = NULL);
+                            const CFX_Matrix& matrix);
 
   CPDF_Image* LoadImageF(CPDF_Object* pObj);
   CPDF_StreamAcc* LoadFontFile(CPDF_Stream* pStream);
   CPDF_IccProfile* LoadIccProfile(CPDF_Stream* pStream);
 
   void LoadDoc();
   void LoadAsynDoc(CPDF_Dictionary* pLinearized);
   void LoadPages();
 
   // Editing methods.
@@ skipping 43 matching lines @@
   bool m_bLinearized;
   int m_iFirstPageNo;
   uint32_t m_dwFirstPageObjNum;
   CFX_ArrayTemplate<uint32_t> m_PageList;
   // TODO(thestig): Figure out why this cannot be a std::unique_ptr.
   CPDF_DocPageData* m_pDocPage;
   std::unique_ptr<CPDF_DocRenderData> m_pDocRender;
 };
 
 #endif  // CORE_FPDFAPI_FPDF_PARSER_INCLUDE_CPDF_DOCUMENT_H_