Cleanup xfa_document_datamerge 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_common_config") {
   cflags = []
@@ skipping 1345 matching lines @@
       "xfa/fxfa/parser/cxfa_tooltip.h",
       "xfa/fxfa/parser/cxfa_validate.cpp",
       "xfa/fxfa/parser/cxfa_validate.h",
       "xfa/fxfa/parser/cxfa_value.cpp",
       "xfa/fxfa/parser/cxfa_value.h",
       "xfa/fxfa/parser/cxfa_valuearray.cpp",
       "xfa/fxfa/parser/cxfa_valuearray.h",
       "xfa/fxfa/parser/cxfa_widgetdata.cpp",
       "xfa/fxfa/parser/cxfa_widgetdata.h",
       "xfa/fxfa/parser/xfa_basic_data.cpp",
+      "xfa/fxfa/parser/xfa_basic_data.h",
       "xfa/fxfa/parser/xfa_basic_data_attributes.cpp",
       "xfa/fxfa/parser/xfa_basic_data_element_attributes.cpp",
       "xfa/fxfa/parser/xfa_basic_data_element_properties.cpp",
       "xfa/fxfa/parser/xfa_basic_data_element_script.cpp",
       "xfa/fxfa/parser/xfa_basic_data_enum.cpp",
       "xfa/fxfa/parser/xfa_basic_data_packets.cpp",
-      "xfa/fxfa/parser/xfa_basic_data.h",
       "xfa/fxfa/parser/xfa_basic_imp.cpp",
       "xfa/fxfa/parser/xfa_basic_imp.h",
       "xfa/fxfa/parser/xfa_doclayout.h",
       "xfa/fxfa/parser/xfa_document.h",
-      "xfa/fxfa/parser/xfa_document_datadescription_imp.cpp",
-      "xfa/fxfa/parser/xfa_document_datadescription_imp.h",
       "xfa/fxfa/parser/xfa_document_datamerger_imp.cpp",
       "xfa/fxfa/parser/xfa_document_datamerger_imp.h",
       "xfa/fxfa/parser/xfa_document_imp.cpp",
       "xfa/fxfa/parser/xfa_document_layout_imp.cpp",
       "xfa/fxfa/parser/xfa_document_layout_imp.h",
       "xfa/fxfa/parser/xfa_document_serialize.cpp",
       "xfa/fxfa/parser/xfa_document_serialize.h",
       "xfa/fxfa/parser/xfa_layout_appadapter.cpp",
       "xfa/fxfa/parser/xfa_layout_appadapter.h",
       "xfa/fxfa/parser/xfa_layout_itemlayout.cpp",
@@ skipping 183 matching lines @@
 }
 
 if (pdf_is_standalone) {
   source_set("samples") {
     testonly = true
     deps = [
       "//samples",
     ]
   }
 }