Remove IXFA_Parser, cleanup XFA parser 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 1377 matching lines @@
       "xfa/fxfa/parser/xfa_layout_pagemgr_new.cpp",
       "xfa/fxfa/parser/xfa_layout_pagemgr_new.h",
       "xfa/fxfa/parser/xfa_locale.cpp",
       "xfa/fxfa/parser/xfa_locale.h",
       "xfa/fxfa/parser/xfa_localemgr.cpp",
       "xfa/fxfa/parser/xfa_localemgr.h",
       "xfa/fxfa/parser/xfa_localevalue.cpp",
       "xfa/fxfa/parser/xfa_localevalue.h",
       "xfa/fxfa/parser/xfa_object.h",
       "xfa/fxfa/parser/xfa_object_imp.cpp",
-      "xfa/fxfa/parser/xfa_parser.h",
       "xfa/fxfa/parser/xfa_parser_imp.cpp",
       "xfa/fxfa/parser/xfa_parser_imp.h",
       "xfa/fxfa/parser/xfa_script.h",
       "xfa/fxfa/parser/xfa_script_datawindow.cpp",
       "xfa/fxfa/parser/xfa_script_datawindow.h",
       "xfa/fxfa/parser/xfa_script_eventpseudomodel.cpp",
       "xfa/fxfa/parser/xfa_script_eventpseudomodel.h",
       "xfa/fxfa/parser/xfa_script_hostpseudomodel.cpp",
       "xfa/fxfa/parser/xfa_script_hostpseudomodel.h",
       "xfa/fxfa/parser/xfa_script_imp.cpp",
@@ skipping 161 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }