Add unit test for CXFA_FileRead.

core/fpdfapi/parser/cpdf_stream.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 "core/fpdfapi/parser/cpdf_stream.h"
 
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
@@ skipping 95 matching lines @@
                               uint32_t size) const {
   if (m_bMemoryBased && m_pFile)
     return m_pFile->ReadBlock(buf, offset, size);
 
   if (m_pDataBuf)
     FXSYS_memcpy(buf, m_pDataBuf.get() + offset, size);
 
   return true;
 }
 
+bool CPDF_Stream::HasFilter() const {
+  return m_pDict && m_pDict->KeyExist("Filter");
+}
+
 CFX_WideString CPDF_Stream::GetUnicodeText() const {
   CPDF_StreamAcc stream;
   stream.LoadAllData(this, false);
   return PDF_DecodeText(stream.GetData(), stream.GetSize());
 }