Move function prototypes to new doc_utils.h file

BUILD.gn

 # Copyright 2014 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("//testing/test.gni")
 
 pdf_use_skia = false
 
 declare_args() {
   # On Android there's no system FreeType. On Windows and Mac, only a few
@@ skipping 157 matching lines @@
     "core/src/fpdfdoc/doc_basic.cpp",
     "core/src/fpdfdoc/doc_bookmark.cpp",
     "core/src/fpdfdoc/doc_form.cpp",
     "core/src/fpdfdoc/doc_formcontrol.cpp",
     "core/src/fpdfdoc/doc_formfield.cpp",
     "core/src/fpdfdoc/doc_link.cpp",
     "core/src/fpdfdoc/doc_metadata.cpp",
     "core/src/fpdfdoc/doc_ocg.cpp",
     "core/src/fpdfdoc/doc_tagged.cpp",
     "core/src/fpdfdoc/doc_utils.cpp",
+    "core/src/fpdfdoc/doc_utils.h",
     "core/src/fpdfdoc/doc_viewerPreferences.cpp",
     "core/src/fpdfdoc/doc_vt.cpp",
     "core/src/fpdfdoc/doc_vtmodule.cpp",
     "core/src/fpdfdoc/pdf_vt.h",
     "core/src/fpdfdoc/tagged_int.h",
   ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     ":pdfium_config",
     "//build/config/compiler:no_chromium_code",
@@ skipping 699 matching lines @@
     "//testing/gtest",
     ":pdfium",
   ]
   include_dirs = [ "." ]
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     ":pdfium_config",
     "//build/config/compiler:no_chromium_code",
   ]
 }