Remove foxitlib.h and foxitxfa.h and IWYU.

xfa.gyp

 {
   "variables": {
     "pdf_enable_v8%": 1,
   },
   "target_defaults": {
     "defines": [
       "PDF_ENABLE_XFA",
     ],
   },
   "targets":[
     {
       "target_name":"xfa",
       "type":"static_library",
       'include_dirs': [
         # This is implicit in GN.
         '<(DEPTH)',
         '.',
         'third_party/freetype/include',
         'third_party/freetype/include/freetype',
       ],
       'defines' : [
         'FT2_BUILD_LIBRARY',
       ],
       "sources":[
-        "xfa/include/foxitxfa.h",
         "xfa/include/fwl/adapter/fwl_adapternative.h",
         "xfa/include/fwl/adapter/fwl_adapterthreadmgr.h",
         "xfa/include/fwl/adapter/fwl_adaptertimermgr.h",
         "xfa/include/fwl/adapter/fwl_adapterwidgetmgr.h",
         "xfa/include/fwl/adapter/fwl_sdadapterimp.h",
         "xfa/include/fwl/basewidget/fwl_barcode.h",
         "xfa/include/fwl/basewidget/fwl_caret.h",
         "xfa/include/fwl/basewidget/fwl_checkbox.h",
         "xfa/include/fwl/basewidget/fwl_combobox.h",
         "xfa/include/fwl/basewidget/fwl_datetimepicker.h",
@@ skipping 147 matching lines @@
         "xfa/src/fgas/src/layout/fx_textbreak.h",
         "xfa/src/fgas/src/layout/fx_unicode.cpp",
         "xfa/src/fgas/src/layout/fx_unicode.h",
         "xfa/src/fgas/src/localization/fx_datetime.cpp",
         "xfa/src/fgas/src/localization/fx_locale.cpp",
         "xfa/src/fgas/src/localization/fx_localeimp.h",
         "xfa/src/fgas/src/localization/fx_localemgr.cpp",
         "xfa/src/fgas/src/localization/fx_localemgr.h",
         "xfa/src/fgas/src/xml/fx_sax_imp.cpp",
         "xfa/src/fgas/src/xml/fx_sax_imp.h",
-        "xfa/src/foxitlib.h",
         "xfa/src/fwl/src/basewidget/fwl_barcodeimp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_caretimp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_checkboximp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_comboboximp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_datetimepickerimp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_editimp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_formproxyimp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_listboximp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_monthcalendarimp.cpp",
         "xfa/src/fwl/src/basewidget/fwl_pictureboximp.cpp",
@@ skipping 486 matching lines @@
           "sources": [],
         }],
         ["OS == 'mac'", {
           "configurations": {},
           "sources": [],
         }],
       ]
     }
   ]
 }