diff --git a/core/fpdfapi/page/cpdf_color.cpp b/core/fpdfapi/page/cpdf_color.cpp
index 59ce6da..6e772aa 100644
--- a/core/fpdfapi/page/cpdf_color.cpp
+++ b/core/fpdfapi/page/cpdf_color.cpp
@@ -31,7 +31,7 @@
     PatternValue* pvalue = (PatternValue*)m_pBuffer;
     CPDF_Pattern* pPattern =
         pvalue->m_pCountedPattern ? pvalue->m_pCountedPattern->get() : nullptr;
-    if (pPattern && pPattern->document()) {
+    if (pPattern) {
       CPDF_DocPageData* pPageData = pPattern->document()->GetPageData();
       if (pPageData)
         pPageData->ReleasePattern(pPattern->pattern_obj());
@@ -89,7 +89,7 @@
 
   CPDF_DocPageData* pDocPageData = nullptr;
   PatternValue* pvalue = (PatternValue*)m_pBuffer;
-  if (pvalue->m_pPattern && pvalue->m_pPattern->document()) {
+  if (pvalue->m_pPattern) {
     pDocPageData = pvalue->m_pPattern->document()->GetPageData();
     if (pDocPageData)
       pDocPageData->ReleasePattern(pvalue->m_pPattern->pattern_obj());
@@ -100,7 +100,7 @@
     memcpy(pvalue->m_Comps, comps, ncomps * sizeof(float));
 
   pvalue->m_pCountedPattern = nullptr;
-  if (pPattern && pPattern->document()) {
+  if (pPattern) {
     if (!pDocPageData)
       pDocPageData = pPattern->document()->GetPageData();
 
@@ -129,7 +129,7 @@
 
   PatternValue* pValue = reinterpret_cast<PatternValue*>(m_pBuffer);
   CPDF_Pattern* pPattern = pValue->m_pPattern;
-  if (pPattern && pPattern->document()) {
+  if (pPattern) {
     pValue->m_pPattern = pPattern->document()->GetPageData()->GetPattern(
         pPattern->pattern_obj(), false, pPattern->parent_matrix());
   }
diff --git a/core/fpdfapi/page/cpdf_docpagedata.cpp b/core/fpdfapi/page/cpdf_docpagedata.cpp
index 5e13740..58e8155 100644
--- a/core/fpdfapi/page/cpdf_docpagedata.cpp
+++ b/core/fpdfapi/page/cpdf_docpagedata.cpp
@@ -28,7 +28,9 @@
 #include "third_party/base/stl_util.h"
 
 CPDF_DocPageData::CPDF_DocPageData(CPDF_Document* pPDFDoc)
-    : m_pPDFDoc(pPDFDoc), m_bForceClear(false) {}
+    : m_pPDFDoc(pPDFDoc), m_bForceClear(false) {
+  assert(m_pPDFDoc);
+}
 
 CPDF_DocPageData::~CPDF_DocPageData() {
   Clear(false);
@@ -330,7 +332,7 @@
     pPattern = pdfium::MakeUnique<CPDF_ShadingPattern>(m_pPDFDoc, pPatternObj,
                                                        true, matrix);
   } else {
-    CPDF_Dictionary* pDict = pPatternObj ? pPatternObj->GetDict() : nullptr;
+    CPDF_Dictionary* pDict = pPatternObj->GetDict();
     if (pDict) {
       int type = pDict->GetIntegerFor("PatternType");
       if (type == CPDF_Pattern::TILING) {
diff --git a/core/fpdfapi/page/cpdf_pattern.cpp b/core/fpdfapi/page/cpdf_pattern.cpp
index b0a2d81..88e5dee 100644
--- a/core/fpdfapi/page/cpdf_pattern.cpp
+++ b/core/fpdfapi/page/cpdf_pattern.cpp
@@ -6,13 +6,17 @@
 
 #include "core/fpdfapi/page/cpdf_pattern.h"
 
-CPDF_Pattern::CPDF_Pattern(PatternType type,
-                           CPDF_Document* pDoc,
+#include "core/fpdfapi/parser/cpdf_dictionary.h"
+
+CPDF_Pattern::CPDF_Pattern(CPDF_Document* pDoc,
                            CPDF_Object* pObj,
                            const CFX_Matrix& parentMatrix)
-    : m_PatternType(type),
-      m_pDocument(pDoc),
-      m_pPatternObj(pObj),
-      m_ParentMatrix(parentMatrix) {}
+    : m_pDocument(pDoc), m_pPatternObj(pObj), m_ParentMatrix(parentMatrix) {}
 
 CPDF_Pattern::~CPDF_Pattern() {}
+
+void CPDF_Pattern::SetPatternToFormMatrix() {
+  CPDF_Dictionary* pDict = pattern_obj()->GetDict();
+  m_Pattern2Form = pDict->GetMatrixFor("Matrix");
+  m_Pattern2Form.Concat(m_ParentMatrix);
+}
diff --git a/core/fpdfapi/page/cpdf_pattern.h b/core/fpdfapi/page/cpdf_pattern.h
index d44965f..3b948ae 100644
--- a/core/fpdfapi/page/cpdf_pattern.h
+++ b/core/fpdfapi/page/cpdf_pattern.h
@@ -24,18 +24,20 @@
   virtual CPDF_TilingPattern* AsTilingPattern() = 0;
   virtual CPDF_ShadingPattern* AsShadingPattern() = 0;
 
+  // All the getters that return pointers return non-NULL pointers.
   CPDF_Document* document() { return m_pDocument; }
   CPDF_Object* pattern_obj() { return m_pPatternObj; }
   CFX_Matrix* pattern_to_form() { return &m_Pattern2Form; }
   const CFX_Matrix& parent_matrix() const { return m_ParentMatrix; }
 
  protected:
-  CPDF_Pattern(PatternType type,
-               CPDF_Document* pDoc,
+  CPDF_Pattern(CPDF_Document* pDoc,
                CPDF_Object* pObj,
                const CFX_Matrix& parentMatrix);
 
-  const PatternType m_PatternType;
+  void SetPatternToFormMatrix();
+
+ private:
   CPDF_Document* const m_pDocument;
   CPDF_Object* const m_pPatternObj;
   CFX_Matrix m_Pattern2Form;
diff --git a/core/fpdfapi/page/cpdf_shadingpattern.cpp b/core/fpdfapi/page/cpdf_shadingpattern.cpp
index 133d32f..dae5ec3 100644
--- a/core/fpdfapi/page/cpdf_shadingpattern.cpp
+++ b/core/fpdfapi/page/cpdf_shadingpattern.cpp
@@ -31,27 +31,23 @@
                                          CPDF_Object* pPatternObj,
                                          bool bShading,
                                          const CFX_Matrix& parentMatrix)
-    : CPDF_Pattern(SHADING,
-                   pDoc,
-                   bShading ? nullptr : pPatternObj,
-                   parentMatrix),
+    : CPDF_Pattern(pDoc, bShading ? nullptr : pPatternObj, parentMatrix),
       m_ShadingType(kInvalidShading),
       m_bShadingObj(bShading),
       m_pShadingObj(pPatternObj),
       m_pCS(nullptr),
       m_pCountedCS(nullptr) {
+  assert(document());
   if (!bShading) {
-    CPDF_Dictionary* pDict = m_pPatternObj->GetDict();
-    m_Pattern2Form = pDict->GetMatrixFor("Matrix");
-    m_pShadingObj = pDict->GetDirectObjectFor("Shading");
-    m_Pattern2Form.Concat(parentMatrix);
+    m_pShadingObj = pattern_obj()->GetDict()->GetDirectObjectFor("Shading");
+    SetPatternToFormMatrix();
   }
 }
 
 CPDF_ShadingPattern::~CPDF_ShadingPattern() {
   CPDF_ColorSpace* pCS = m_pCountedCS ? m_pCountedCS->get() : nullptr;
-  if (pCS && m_pDocument) {
-    auto* pPageData = m_pDocument->GetPageData();
+  if (pCS) {
+    auto* pPageData = document()->GetPageData();
     if (pPageData)
       pPageData->ReleaseColorSpace(pCS->GetArray());
   }
@@ -89,7 +85,7 @@
   if (!pCSObj)
     return false;
 
-  CPDF_DocPageData* pDocPageData = m_pDocument->GetPageData();
+  CPDF_DocPageData* pDocPageData = document()->GetPageData();
   m_pCS = pDocPageData->GetColorSpace(pCSObj, nullptr);
   if (m_pCS)
     m_pCountedCS = pDocPageData->FindColorSpacePtr(m_pCS->GetArray());
diff --git a/core/fpdfapi/page/cpdf_tilingpattern.cpp b/core/fpdfapi/page/cpdf_tilingpattern.cpp
index a68b442..65542a2 100644
--- a/core/fpdfapi/page/cpdf_tilingpattern.cpp
+++ b/core/fpdfapi/page/cpdf_tilingpattern.cpp
@@ -15,11 +15,10 @@
 CPDF_TilingPattern::CPDF_TilingPattern(CPDF_Document* pDoc,
                                        CPDF_Object* pPatternObj,
                                        const CFX_Matrix& parentMatrix)
-    : CPDF_Pattern(TILING, pDoc, pPatternObj, parentMatrix) {
-  CPDF_Dictionary* pDict = m_pPatternObj->GetDict();
-  m_Pattern2Form = pDict->GetMatrixFor("Matrix");
-  m_bColored = pDict->GetIntegerFor("PaintType") == 1;
-  m_Pattern2Form.Concat(parentMatrix);
+    : CPDF_Pattern(pDoc, pPatternObj, parentMatrix) {
+  assert(document());
+  m_bColored = pattern_obj()->GetDict()->GetIntegerFor("PaintType") == 1;
+  SetPatternToFormMatrix();
 }
 
 CPDF_TilingPattern::~CPDF_TilingPattern() {}
@@ -36,20 +35,21 @@
   if (m_pForm)
     return true;
 
-  CPDF_Dictionary* pDict = m_pPatternObj->GetDict();
+  CPDF_Dictionary* pDict = pattern_obj()->GetDict();
   if (!pDict)
     return false;
 
   m_bColored = pDict->GetIntegerFor("PaintType") == 1;
-  m_XStep = (float)fabs(pDict->GetNumberFor("XStep"));
-  m_YStep = (float)fabs(pDict->GetNumberFor("YStep"));
+  m_XStep = static_cast<float>(fabs(pDict->GetNumberFor("XStep")));
+  m_YStep = static_cast<float>(fabs(pDict->GetNumberFor("YStep")));
 
-  CPDF_Stream* pStream = m_pPatternObj->AsStream();
+  CPDF_Stream* pStream = pattern_obj()->AsStream();
   if (!pStream)
     return false;
 
-  m_pForm = pdfium::MakeUnique<CPDF_Form>(m_pDocument, nullptr, pStream);
-  m_pForm->ParseContent(nullptr, &m_ParentMatrix, nullptr);
+  const CFX_Matrix& matrix = parent_matrix();
+  m_pForm = pdfium::MakeUnique<CPDF_Form>(document(), nullptr, pStream);
+  m_pForm->ParseContent(nullptr, &matrix, nullptr);
   m_BBox = pDict->GetRectFor("BBox");
   return true;
 }