Make concrete stream classes private to .cpp, part 4.

fpdfsdk/cpdfsdk_formfillenvironment.cpp

 // Copyright 2016 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 "fpdfsdk/cpdfsdk_formfillenvironment.h"
 
 #include <memory>
 
@@ skipping 455 matching lines @@
     const FX_WCHAR* url) {
   if (!m_pInfo || !m_pInfo->FFI_DownloadFromURL)
     return nullptr;
 
   CFX_ByteString bstrURL = CFX_WideString(url).UTF16LE_Encode();
   FPDF_WIDESTRING wsURL =
       (FPDF_WIDESTRING)bstrURL.GetBuffer(bstrURL.GetLength());
 
   FPDF_LPFILEHANDLER fileHandler = m_pInfo->FFI_DownloadFromURL(m_pInfo, wsURL);
 
-  return new CFPDF_FileStream(fileHandler);
+  return MakeSeekableStream(fileHandler);
 }
 
 CFX_WideString CPDFSDK_FormFillEnvironment::PostRequestURL(
     const FX_WCHAR* wsURL,
     const FX_WCHAR* wsData,
     const FX_WCHAR* wsContentType,
     const FX_WCHAR* wsEncode,
     const FX_WCHAR* wsHeader) {
   if (!m_pInfo || !m_pInfo->FFI_PostRequestURL)
     return L"";
@@ skipping 266 matching lines @@
     } else {
       m_pFocusAnnot.Reset(pFocusAnnot.Get());
     }
   }
   return false;
 }
 
 bool CPDFSDK_FormFillEnvironment::GetPermissions(int nFlag) {
   return !!(GetPDFDocument()->GetUserPermissions() & nFlag);
 }