Introduce "underlying types" to abstract XFA differences.

fpdfsdk/src/javascript/app.cpp

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "app.h"
 
 #include "Document.h"
 #include "JS_Context.h"
@@ skipping 182 matching lines @@
 }
 
 FX_BOOL app::viewerVersion(IJS_Context* cc,
                            CJS_PropValue& vp,
                            CFX_WideString& sError) {
   if (!vp.IsGetting())
     return FALSE;
 
   CJS_Context* pContext = (CJS_Context*)cc;
   CPDFSDK_Document* pCurDoc = pContext->GetReaderDocument();
-  CPDFXFA_Document* pDoc = pCurDoc->GetDocument();
+  CPDFXFA_Document* pDoc = pCurDoc->GetXFADocument();
   if (pDoc->GetDocType() == 1 || pDoc->GetDocType() == 2) {
     vp << JS_NUM_VIEWERVERSION_XFA;
     return TRUE;
   }
 
   vp << JS_NUM_VIEWERVERSION;
   return TRUE;
 }
 
 FX_BOOL app::platform(IJS_Context* cc,
@@ skipping 596 matching lines @@
 FX_BOOL app::media(IJS_Context* cc, CJS_PropValue& vp, CFX_WideString& sError) {
   return FALSE;
 }
 
 FX_BOOL app::execDialog(IJS_Context* cc,
                         const std::vector<CJS_Value>& params,
                         CJS_Value& vRet,
                         CFX_WideString& sError) {
   return TRUE;
 }