Add APIs for limited use of document tagged code.

fpdfsdk/fpdfview_c_api_test.c

 // Copyright 2015 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.
 
 // This "C" (not "C++") file ensures that the public headers compile
 // and link for "C" (and not just "C++").
 
 #include <stdio.h>
 
 #include "fpdfsdk/fpdfview_c_api_test.h"
 
 #include "public/fpdf_dataavail.h"
 #include "public/fpdf_doc.h"
 #include "public/fpdf_edit.h"
 #include "public/fpdf_ext.h"
 #include "public/fpdf_flatten.h"
 #include "public/fpdf_formfill.h"
 #include "public/fpdf_fwlevent.h"
 #include "public/fpdf_ppo.h"
 #include "public/fpdf_progressive.h"
 #include "public/fpdf_save.h"
 #include "public/fpdf_searchex.h"
+#include "public/fpdf_structtree.h"
 #include "public/fpdf_sysfontinfo.h"
 #include "public/fpdf_text.h"
 #include "public/fpdf_transformpage.h"
 #include "public/fpdfview.h"
 
 // Scheme for avoiding LTO out of existence, warnings, etc.
 typedef void (*fnptr)(void);  // Legal generic function type for casts.
 fnptr g_c_api_test_fnptr = NULL;  // Extern, so can't know it doesn't change.
 #define CHK(x) if ((fnptr)(x) == g_c_api_test_fnptr) return 0
 
@@ skipping 113 matching lines @@
     CHK(FPDF_RenderPage_Continue);
     CHK(FPDF_RenderPage_Close);
 
     // fpdf_save.h
     CHK(FPDF_SaveAsCopy);
     CHK(FPDF_SaveWithVersion);
 
     // fpdf_searchex.h
     CHK(FPDFText_GetCharIndexFromTextIndex);
 
+    // fpdf_structtree.h
+    CHK(FPDF_StructTree_GetForPage);
+    CHK(FPDF_StructTree_Close);
+    CHK(FPDF_StructTree_CountChildren);
+    CHK(FPDF_StructTree_GetChildAtIndex);
+    CHK(FPDF_StructElement_GetAltText);
+    CHK(FPDF_StructElement_CountChildren);
+    CHK(FPDF_StructElement_GetChildAtIndex);
+
     // fpdf_sysfontinfo.h
     CHK(FPDF_GetDefaultTTFMap);
     CHK(FPDF_AddInstalledFont);
     CHK(FPDF_SetSystemFontInfo);
     CHK(FPDF_GetDefaultSystemFontInfo);
     CHK(FPDF_FreeDefaultSystemFontInfo);
 
     // fpdf_text.h
     CHK(FPDFText_LoadPage);
     CHK(FPDFText_ClosePage);
@@ skipping 71 matching lines @@
 #ifdef PDF_ENABLE_XFA
     CHK(FPDF_BStr_Init);
     CHK(FPDF_BStr_Set);
     CHK(FPDF_BStr_Clear);
 #endif
 
     return 1;
 }
 
 #undef CHK