Fix partial information printed with blank window covering the center

core/src/fpdfapi/fpdf_page/fpdf_page_parser.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 "pageint.h"
 
 #include "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_page.h"
@@ skipping 692 matching lines @@
   CFX_ByteStringC type = pXObject->GetDict()
                              ? pXObject->GetDict()->GetConstString("Subtype")
                              : CFX_ByteStringC();
   if (type == "Image") {
     if (m_Options.m_bTextOnly) {
       return;
     }
     CPDF_ImageObject* pObj = AddImage(pXObject, NULL, FALSE);
     m_LastImageName = name;
     m_pLastImage = pObj->m_pImage;
+    if (!m_pObjectList->m_bHasImageMask)
+      m_pObjectList->m_bHasImageMask = m_pLastImage->IsMask();
   } else if (type == "Form") {
     AddForm(pXObject);
   } else {
     return;
   }
 }
 void CPDF_StreamContentParser::AddForm(CPDF_Stream* pStream) {
   if (!m_Options.m_bSeparateForm) {
     CPDF_Dictionary* pResources = pStream->GetDict()->GetDict("Resources");
     CFX_Matrix form_matrix = pStream->GetDict()->GetMatrix("Matrix");
@@ skipping 795 matching lines @@
     m_pObjectList->m_ObjectList.AddTail(pPathObj);
   }
   if (PathClipType) {
     if (!matrix.IsIdentity()) {
       Path.Transform(&matrix);
       matrix.SetIdentity();
     }
     m_pCurStates->m_ClipPath.AppendPath(Path, PathClipType, TRUE);
   }
 }