Clean up CPDF_Page.

core/fpdfapi/fpdf_page/cpdf_shadingpattern.h

Index: core/fpdfapi/fpdf_page/cpdf_shadingpattern.h
diff --git a/core/fpdfapi/fpdf_page/cpdf_shadingpattern.h b/core/fpdfapi/fpdf_page/cpdf_shadingpattern.h
index c9bbd07d2e560c0c962e4e4a102b673fb7c3b5fb..7e5a24d4fec0b47bb5b54ce6132787c6956e208b 100644
--- a/core/fpdfapi/fpdf_page/cpdf_shadingpattern.h
+++ b/core/fpdfapi/fpdf_page/cpdf_shadingpattern.h
@@ -12,7 +12,7 @@
 #include "core/fpdfapi/fpdf_page/pageint.h"
 #include "core/fxcrt/include/fx_system.h"
 
-typedef enum {
+enum ShadingType {
   kInvalidShading = 0,
   kFunctionBasedShading = 1,
   kAxialShading = 2,
@@ -22,7 +22,7 @@ typedef enum {
   kCoonsPatchMeshShading = 6,
   kTensorProductPatchMeshShading = 7,
   kMaxShading = 8
-} ShadingType;
+};
 
 class CFX_Matrix;
 class CPDF_ColorSpace;
@@ -38,6 +38,9 @@ class CPDF_ShadingPattern : public CPDF_Pattern {
 
   ~CPDF_ShadingPattern() override;
 
+  CPDF_TilingPattern* AsTilingPattern() override { return nullptr; }
+  CPDF_ShadingPattern* AsShadingPattern() override { return this; }
+
   bool IsMeshShading() const {
     return m_ShadingType == kFreeFormGouraudTriangleMeshShading ||
            m_ShadingType == kLatticeFormGouraudTriangleMeshShading ||