Cleanup xfa_document_datamerge files

xfa.gyp

 {
   "variables": {
     "chromium_code": 1,
     "pdf_enable_v8%": 1,
      "variables": {
       'clang_use_chrome_plugins': 1,
     },
   },
   "target_defaults": {
     "defines": [
@@ skipping 506 matching lines @@
         "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 73 matching lines @@
           "sources": [],
         }],
         ["OS == 'mac'", {
           "configurations": {},
           "sources": [],
         }],
       ]
     }
   ]
 }