Move some classes out of doc_vt.cpp into their own files.

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_config") {
   cflags = []
@@ skipping 188 matching lines @@
     "core/fpdfdoc/cpvt_color.h",
     "core/fpdfdoc/cpvt_dash.h",
     "core/fpdfdoc/cpvt_floatrect.h",
     "core/fpdfdoc/cpvt_fontmap.cpp",
     "core/fpdfdoc/cpvt_fontmap.h",
     "core/fpdfdoc/cpvt_generateap.cpp",
     "core/fpdfdoc/cpvt_generateap.h",
     "core/fpdfdoc/cpvt_lineinfo.h",
     "core/fpdfdoc/cpvt_sectioninfo.h",
     "core/fpdfdoc/cpvt_wordinfo.h",
+    "core/fpdfdoc/csection.cpp",
     "core/fpdfdoc/csection.h",
+    "core/fpdfdoc/ctypeset.cpp",
     "core/fpdfdoc/ctypeset.h",
     "core/fpdfdoc/doc_action.cpp",
     "core/fpdfdoc/doc_annot.cpp",
     "core/fpdfdoc/doc_basic.cpp",
     "core/fpdfdoc/doc_bookmark.cpp",
     "core/fpdfdoc/doc_form.cpp",
     "core/fpdfdoc/doc_formcontrol.cpp",
     "core/fpdfdoc/doc_formfield.cpp",
     "core/fpdfdoc/doc_link.cpp",
     "core/fpdfdoc/doc_metadata.cpp",
@@ skipping 1473 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }