Cleanup CPDF_StructElement.

fpdfsdk/fpdf_structtree.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.
 
 #include "public/fpdf_structtree.h"
 
 #include "core/fpdfapi/page/cpdf_page.h"
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfdoc/fpdf_tagged.h"
 #include "fpdfsdk/fsdk_define.h"
@@ skipping 65 matching lines @@
   return elem ? elem->CountKids() : -1;
 }
 
 DLLEXPORT FPDF_STRUCTELEMENT STDCALL
 FPDF_StructElement_GetChildAtIndex(FPDF_STRUCTELEMENT struct_element,
                                    int index) {
   IPDF_StructElement* elem = ToStructTreeElement(struct_element);
   if (!elem || index < 0 || index >= elem->CountKids())
     return nullptr;
 
-  CPDF_StructKid kid = elem->GetKid(index);
-  return kid.m_Type == CPDF_StructKid::Element ? kid.m_Element.m_pElement
-                                               : nullptr;
+  return elem->GetKidIfElement(index);
 }