Add APIs for limited use of document tagged code.

BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build_overrides/v8.gni")
 import("//testing/test.gni")
 import("pdfium.gni")
 
 config("pdfium_common_config") {
   cflags = []
@@ skipping 79 matching lines @@
     "fpdfsdk/cpdfsdk_pageview.h",
     "fpdfsdk/cpdfsdk_widget.cpp",
     "fpdfsdk/cpdfsdk_widget.h",
     "fpdfsdk/cpdfsdk_widgethandler.cpp",
     "fpdfsdk/cpdfsdk_widgethandler.h",
     "fpdfsdk/fpdf_dataavail.cpp",
     "fpdfsdk/fpdf_ext.cpp",
     "fpdfsdk/fpdf_flatten.cpp",
     "fpdfsdk/fpdf_progressive.cpp",
     "fpdfsdk/fpdf_searchex.cpp",
+    "fpdfsdk/fpdf_structtree.cpp",
     "fpdfsdk/fpdf_sysfontinfo.cpp",
     "fpdfsdk/fpdf_transformpage.cpp",
     "fpdfsdk/fpdfdoc.cpp",
     "fpdfsdk/fpdfeditimg.cpp",
     "fpdfsdk/fpdfeditpage.cpp",
     "fpdfsdk/fpdfformfill.cpp",
     "fpdfsdk/fpdfppo.cpp",
     "fpdfsdk/fpdfsave.cpp",
     "fpdfsdk/fpdftext.cpp",
     "fpdfsdk/fpdfview.cpp",
     "fpdfsdk/fsdk_actionhandler.cpp",
     "fpdfsdk/fsdk_actionhandler.h",
     "fpdfsdk/fsdk_pauseadapter.cpp",
     "fpdfsdk/fsdk_pauseadapter.h",
     "fpdfsdk/pdfsdk_fieldaction.cpp",
     "fpdfsdk/pdfsdk_fieldaction.h",
     "public/fpdf_dataavail.h",
     "public/fpdf_doc.h",
     "public/fpdf_edit.h",
     "public/fpdf_ext.h",
     "public/fpdf_flatten.h",
     "public/fpdf_formfill.h",
     "public/fpdf_fwlevent.h",
     "public/fpdf_ppo.h",
     "public/fpdf_progressive.h",
     "public/fpdf_save.h",
     "public/fpdf_searchex.h",
+    "public/fpdf_structtree.h",
     "public/fpdf_sysfontinfo.h",
     "public/fpdf_text.h",
     "public/fpdf_transformpage.h",
     "public/fpdfview.h",
   ]
 
   libs = []
   configs += [ ":pdfium_core_config" ]
 
   deps = [
@@ skipping 1653 matching lines @@
     "core/fpdfapi/page/fpdf_page_func_embeddertest.cpp",
     "core/fpdfapi/parser/cpdf_parser_embeddertest.cpp",
     "core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp",
     "core/fpdfapi/parser/fpdf_parser_decode_embeddertest.cpp",
     "core/fpdfapi/render/fpdf_render_loadimage_embeddertest.cpp",
     "core/fpdfapi/render/fpdf_render_pattern_embeddertest.cpp",
     "core/fxcodec/codec/fx_codec_embeddertest.cpp",
     "core/fxge/ge/fx_ge_text_embeddertest.cpp",
     "fpdfsdk/fpdf_dataavail_embeddertest.cpp",
     "fpdfsdk/fpdf_flatten_embeddertest.cpp",
+    "fpdfsdk/fpdf_structtree_embeddertest.cpp",
     "fpdfsdk/fpdfdoc_embeddertest.cpp",
     "fpdfsdk/fpdfedit_embeddertest.cpp",
     "fpdfsdk/fpdfext_embeddertest.cpp",
     "fpdfsdk/fpdfformfill_embeddertest.cpp",
     "fpdfsdk/fpdfppo_embeddertest.cpp",
     "fpdfsdk/fpdfsave_embeddertest.cpp",
     "fpdfsdk/fpdftext_embeddertest.cpp",
     "fpdfsdk/fpdfview_c_api_test.c",
     "fpdfsdk/fpdfview_c_api_test.h",
     "fpdfsdk/fpdfview_embeddertest.cpp",
@@ skipping 36 matching lines @@
       "//samples",
     ]
   }
   group("fuzzers") {
     testonly = true
     deps = [
       "//testing/libfuzzer",
     ]
   }
 }