Introduce "underlying types" to abstract XFA differences.

fpdfsdk/src/fpdfformfill.cpp

Index: fpdfsdk/src/fpdfformfill.cpp
diff --git a/fpdfsdk/src/fpdfformfill.cpp b/fpdfsdk/src/fpdfformfill.cpp
index 11290eef8bc24386a0ef2bb9342dec0a4cfa458b..a1e807224d69a7e43f060af85b78e9735a7fc2e9 100644
--- a/fpdfsdk/src/fpdfformfill.cpp
+++ b/fpdfsdk/src/fpdfformfill.cpp
@@ -611,8 +611,8 @@ DLLEXPORT void STDCALL FORM_OnBeforeClosePage(FPDF_PAGE page,
   CPDFSDK_PageView* pPageView = pSDKDoc->GetPageView(pPage, FALSE);
   if (pPageView) {
     pPageView->SetValid(FALSE);
-    // ReMovePageView() takes care of the delete for us.
-    pSDKDoc->ReMovePageView(pPage);
+    // RemovePageView() takes care of the delete for us.
+    pSDKDoc->RemovePageView(pPage);
   }
 }
 
@@ -634,7 +634,7 @@ DLLEXPORT void STDCALL FORM_DoDocumentAAction(FPDF_FORMHANDLE hHandle,
   if (!pSDKDoc)
     return;
 
-  CPDF_Document* pDoc = pSDKDoc->GetDocument()->GetPDFDoc();
+  CPDF_Document* pDoc = pSDKDoc->GetPDFDocument();
   CPDF_Dictionary* pDic = pDoc->GetRoot();
   if (!pDic)
     return;