Remove android system expat support.

third_party/expat/BUILD.gn

 # Copyright (c) 2013 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.
 
-if (is_android) {
-  import("//build/config/android/config.gni")
-}
-
 if (is_linux) {
   config("expat_config") {
     libs = [ "expat" ]
   }
 
   group("expat") {
     direct_dependent_configs = [ ":expat_config" ]
   }
-
-  # TODO(GYP) Android needs direct dependent includes of
-  # <android_src>/external/expat/lib
 } else {
   config("expat_config") {
     include_dirs = [ "files/lib" ]
-    if (is_android) {
-      include_dirs += [ "$android_src/external/expat/lib" ]
-    }
     defines = [ "XML_STATIC" ]
   }
 
   static_library("expat") {
     sources = [
       "files/lib/expat.h",
       "files/lib/xmlparse.c",
       "files/lib/xmlrole.c",
       "files/lib/xmltok.c",
     ]
 
     direct_dependent_configs = [ ":expat_config" ]
 
     defines = [ "_LIB" ]
     if (is_win) {
       defines += [ "COMPILED_FROM_DSP" ]
     } else {
       defines += [ "HAVE_EXPAT_CONFIG_H" ]
     }
   }
 }