headless: Add gn settings for embedded build and headless mode

build/linux/BUILD.gn

 # Copyright (c) 2015 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/config/features.gni")
 import("//build/config/linux/pkg_config.gni")
 import("//tools/generate_library_loader/generate_library_loader.gni")
 
 gypi_values = exec_script("//build/gypi_to_gn.py",
                           [ rebase_path("system.gyp") ],
@@ skipping 12 matching lines @@
   generate_library_loader("libbrlapi") {
     name = "LibBrlapiLoader"
     output_h = "libbrlapi.h"
     output_cc = "libbrlapi_loader.cc"
     header = "<brlapi.h>"
     config = ":brlapi_config"
 
     functions = gypi_values.libbrlapi_functions
   }
 }
-if (is_desktop_linux) {
+if (use_gio) {
   pkg_config("gio_config") {
     packages = [ "gio-2.0" ]
 
     # glib >=2.40 deprecate g_settings_list_schemas in favor of
     # g_settings_schema_source_list_schemas. This function is not available on
     # earlier versions that we still need to support (specifically, 2.32), so
     # disable the warning with the GLIB_DISABLE_DEPRECATION_WARNINGS define.
     # TODO(mgiuca): Remove this suppression when we drop support for Ubuntu
     # 13.10 (saucy) and earlier. Update the code to use
     # g_settings_schema_source_list_schemas instead.
@@ skipping 64 matching lines @@
 
 group("fontconfig") {
   if (use_system_fontconfig) {
     public_configs = [ "//build/config/linux:fontconfig" ]
   } else {
     public_deps = [
       "//third_party/fontconfig",
     ]
   }
 }