Add type cast definitions for CPDF_Boolean.

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 4141ec854a5b9800aca60a581ef72e3f52b64078..a52132f6b96885286b56b0068e1cb5b12698d1e1 100644
--- a/core/include/fpdfapi/fpdf_objects.h
+++ b/core/include/fpdfapi/fpdf_objects.h
@@ -78,8 +78,12 @@ class CPDF_Object {
 
   FX_BOOL IsModified() const { return FALSE; }
 
+  bool IsBoolean() const { return m_Type == PDFOBJ_BOOLEAN; }
   bool IsDictionary() const { return m_Type == PDFOBJ_DICTIONARY; }
 
+  CPDF_Boolean* AsBoolean();
+  const CPDF_Boolean* AsBoolean() const;
+
   CPDF_Dictionary* AsDictionary();
   const CPDF_Dictionary* AsDictionary() const;
 
@@ -117,6 +121,13 @@ class CPDF_Boolean : public CPDF_Object {
   FX_BOOL m_bValue;
   friend class CPDF_Object;
 };
+inline CPDF_Boolean* ToBoolean(CPDF_Object* obj) {
+  return obj ? obj->AsBoolean() : nullptr;
+}
+inline const CPDF_Boolean* ToBoolean(const CPDF_Object* obj) {
+  return obj ? obj->AsBoolean() : nullptr;
+}
+
 class CPDF_Number : public CPDF_Object {
  public:
   static CPDF_Number* Create(int value) { return new CPDF_Number(value); }