Revert "Revert "Add type cast definitions for CPDF_Reference.""

fpdfsdk/src/fpdf_flatten.cpp

Index: fpdfsdk/src/fpdf_flatten.cpp
diff --git a/fpdfsdk/src/fpdf_flatten.cpp b/fpdfsdk/src/fpdf_flatten.cpp
index 39441c4aef00c7907d112d282d0915df379b7d4c..75db8f806df5999c15c5d8db8fd49f3baf90e923 100644
--- a/fpdfsdk/src/fpdf_flatten.cpp
+++ b/fpdfsdk/src/fpdf_flatten.cpp
@@ -444,12 +444,10 @@ DLLEXPORT int STDCALL FPDFPage_Flatten(FPDF_PAGE page, int nFlag) {
           CFX_ByteString sKey;
           CPDF_Object* pFirstObj = pAPDic->GetNextElement(pos, sKey);
           if (pFirstObj) {
-            if (pFirstObj->GetType() == PDFOBJ_REFERENCE)
+            if (pFirstObj->IsReference())
               pFirstObj = pFirstObj->GetDirect();
-
             if (!pFirstObj->IsStream())
               continue;
-
             pAPStream = pFirstObj->AsStream();
           }
         }