Replace CFXJSE_HostObject::type_ with polymorphic conversion methods

More foolproof technique, and saves one word in every instance at a
cost of two pointers in every subclass vtable.

Change-Id: Ied4f91d4d203b5e6d83abe751159eb7e55489bb5
Reviewed-on: https://pdfium-review.googlesource.com/38530
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

2 files changed, 9 insertions, 3 deletions

diff --git a/xfa/fxfa/parser/cxfa_object.cpp b/xfa/fxfa/parser/cxfa_object.cpp
index a716c651f5..920e33860e 100644
--- a/xfa/fxfa/parser/cxfa_object.cpp
+++ b/xfa/fxfa/parser/cxfa_object.cpp
@@ -22,15 +22,18 @@ CXFA_Object::CXFA_Object(CXFA_Document* pDocument,
                          XFA_Element elementType,
                          const WideStringView& elementName,
                          std::unique_ptr<CJX_Object> jsObject)
-    : CFXJSE_HostObject(kXFA),
-      m_pDocument(pDocument),
+    : m_pDocument(pDocument),
       m_objectType(objectType),
       m_elementType(elementType),
       m_elementNameHash(FX_HashCode_GetW(elementName, false)),
       m_elementName(elementName),
       m_pJSObject(std::move(jsObject)) {}
 
-CXFA_Object::~CXFA_Object() {}
+CXFA_Object::~CXFA_Object() = default;
+
+CXFA_Object* CXFA_Object::AsCXFAObject() {
+  return this;
+}
 
 WideString CXFA_Object::GetSOMExpression() {
   CFXJSE_Engine* pScriptContext = m_pDocument->GetScriptContext();
diff --git a/xfa/fxfa/parser/cxfa_object.h b/xfa/fxfa/parser/cxfa_object.h
index 20412dcbf7..023516a05e 100644
--- a/xfa/fxfa/parser/cxfa_object.h
+++ b/xfa/fxfa/parser/cxfa_object.h
@@ -36,6 +36,9 @@ class CXFA_Object : public CFXJSE_HostObject {
  public:
   ~CXFA_Object() override;
 
+  // CFXJSE_HostObject:
+  CXFA_Object* AsCXFAObject() override;
+
   CXFA_Document* GetDocument() const { return m_pDocument.Get(); }
   XFA_ObjectType GetObjectType() const { return m_objectType; }