[Merge to XFA] Add type cast definitions for CPDF_Boolean.

This CL adds ToBoolean, CPDF_Object::AsBoolean and CPDF_Object::IsBoolean and
updates the src to use them as needed.

BUG=pdfium:201
TBR=thestig@chromium.org, tsepez@chromium.org

Review URL: https://codereview.chromium.org/1417623005 .

(cherry picked from commit ce4f95d61f5aa5fb9a5fc6cb8487999a9cf46458)

Review URL: https://codereview.chromium.org/1419663004 .

2 files changed, 25 insertions, 7 deletions

diff --git a/core/include/fpdfapi/fpdf_objects.h b/core/include/fpdfapi/fpdf_objects.h
index d64a0924f8..a5f52832a1 100644
--- a/core/include/fpdfapi/fpdf_objects.h
+++ b/core/include/fpdfapi/fpdf_objects.h
@@ -80,8 +80,12 @@ 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;
 
@@ -119,6 +123,13 @@ 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); }
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_objects.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_objects.cpp
index 55c274ac0f..8afa011585 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_objects.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_objects.cpp
@@ -40,7 +40,7 @@ void CPDF_Object::Destroy() {
 CFX_ByteString CPDF_Object::GetString() const {
   switch (m_Type) {
     case PDFOBJ_BOOLEAN:
-      return ((CPDF_Boolean*)this)->m_bValue ? "true" : "false";
+      return AsBoolean()->m_bValue ? "true" : "false";
     case PDFOBJ_NUMBER:
       return ((CPDF_Number*)this)->GetString();
     case PDFOBJ_STRING:
@@ -114,7 +114,7 @@ int CPDF_Object::GetInteger() const {
   }
   switch (m_Type) {
     case PDFOBJ_BOOLEAN:
-      return ((CPDF_Boolean*)this)->m_bValue;
+      return this->AsBoolean()->m_bValue;
     case PDFOBJ_NUMBER:
       return ((CPDF_Number*)this)->GetInteger();
     case PDFOBJ_REFERENCE: {
@@ -168,7 +168,7 @@ void CPDF_Object::SetString(const CFX_ByteString& str) {
   ASSERT(this != NULL);
   switch (m_Type) {
     case PDFOBJ_BOOLEAN:
-      ((CPDF_Boolean*)this)->m_bValue = str == FX_BSTRC("true") ? 1 : 0;
+      AsBoolean()->m_bValue = (str == FX_BSTRC("true"));
       return;
     case PDFOBJ_NUMBER:
       ((CPDF_Number*)this)->SetString(str);
@@ -207,7 +207,7 @@ FX_BOOL CPDF_Object::IsIdentical(CPDF_Object* pOther) const {
   }
   switch (m_Type) {
     case PDFOBJ_BOOLEAN:
-      return (((CPDF_Boolean*)this)->Identical((CPDF_Boolean*)pOther));
+      return this->AsBoolean()->Identical(pOther->AsBoolean());
     case PDFOBJ_NUMBER:
       return (((CPDF_Number*)this)->Identical((CPDF_Number*)pOther));
     case PDFOBJ_STRING:
@@ -245,7 +245,7 @@ CPDF_Object* CPDF_Object::CloneInternal(FX_BOOL bDirect,
                                         CFX_MapPtrToPtr* visited) const {
   switch (m_Type) {
     case PDFOBJ_BOOLEAN:
-      return new CPDF_Boolean(((CPDF_Boolean*)this)->m_bValue);
+      return new CPDF_Boolean(this->AsBoolean()->m_bValue);
     case PDFOBJ_NUMBER:
       return new CPDF_Number(((CPDF_Number*)this)->m_bInteger,
                              &((CPDF_Number*)this)->m_Integer);
@@ -337,6 +337,14 @@ void CPDF_Object::SetUnicodeText(const FX_WCHAR* pUnicodes, int len) {
   }
 }
 
+CPDF_Boolean* CPDF_Object::AsBoolean() {
+  return IsBoolean() ? static_cast<CPDF_Boolean*>(this) : nullptr;
+}
+
+const CPDF_Boolean* CPDF_Object::AsBoolean() const {
+  return IsBoolean() ? static_cast<const CPDF_Boolean*>(this) : nullptr;
+}
+
 CPDF_Dictionary* CPDF_Object::AsDictionary() {
   return IsDictionary() ? static_cast<CPDF_Dictionary*>(this) : nullptr;
 }
@@ -663,9 +671,8 @@ FX_BOOL CPDF_Dictionary::GetBoolean(const CFX_ByteStringC& key,
                                     FX_BOOL bDefault) const {
   CPDF_Object* p = NULL;
   m_Map.Lookup(key, (void*&)p);
-  if (p && p->GetType() == PDFOBJ_BOOLEAN) {
+  if (ToBoolean(p))
     return p->GetInteger();
-  }
   return bDefault;
 }
 CPDF_Dictionary* CPDF_Dictionary::GetDict(const CFX_ByteStringC& key) const {