Add type cast definitions for CPDF_Number.

core/include/fpdfapi/fpdf_objects.h

Index: core/include/fpdfapi/fpdf_objects.h
diff --git a/core/include/fpdfapi/fpdf_objects.h b/core/include/fpdfapi/fpdf_objects.h
index 0df8be727cb9019fdc1dfba16b70dbac8dd44195..438c89cc50121bc201d6fc5882bd281e3af1b031 100644
--- a/core/include/fpdfapi/fpdf_objects.h
+++ b/core/include/fpdfapi/fpdf_objects.h
@@ -80,6 +80,7 @@ class CPDF_Object {
 
   bool IsBoolean() const { return m_Type == PDFOBJ_BOOLEAN; }
   bool IsDictionary() const { return m_Type == PDFOBJ_DICTIONARY; }
+  bool IsNumber() const { return m_Type == PDFOBJ_NUMBER; }
 
   CPDF_Boolean* AsBoolean();
   const CPDF_Boolean* AsBoolean() const;
@@ -87,6 +88,9 @@ class CPDF_Object {
   CPDF_Dictionary* AsDictionary();
   const CPDF_Dictionary* AsDictionary() const;
 
+  CPDF_Number* AsNumber();
+  const CPDF_Number* AsNumber() const;
+
  protected:
   CPDF_Object(FX_DWORD type) : m_Type(type), m_ObjNum(0), m_GenNum(0) {}
   ~CPDF_Object() {}
@@ -178,6 +182,13 @@ class CPDF_Number : public CPDF_Object {
   };
   friend class CPDF_Object;
 };
+inline CPDF_Number* ToNumber(CPDF_Object* obj) {
+  return obj ? obj->AsNumber() : nullptr;
+}
+inline const CPDF_Number* ToNumber(const CPDF_Object* obj) {
+  return obj ? obj->AsNumber() : nullptr;
+}
+
 class CPDF_String : public CPDF_Object {
  public:
   static CPDF_String* Create(const CFX_ByteString& str, FX_BOOL bHex = FALSE) {