Use org.gnome.desktop.interface text-scaling-factor directly

chrome/browser/ui/libgtk2ui/BUILD.gn

Index: chrome/browser/ui/libgtk2ui/BUILD.gn
diff --git a/chrome/browser/ui/libgtk2ui/BUILD.gn b/chrome/browser/ui/libgtk2ui/BUILD.gn
index b85f67d988321d338ec7b8ed986d1b573c21e7e0..b89e3d28c08f40d38f714cea756e01584f7b703d 100644
--- a/chrome/browser/ui/libgtk2ui/BUILD.gn
+++ b/chrome/browser/ui/libgtk2ui/BUILD.gn
@@ -61,7 +61,14 @@ component("libgtk2ui") {
       "gconf_listener.h",
     ]
   }
-  defines = [ "LIBGTK2UI_IMPLEMENTATION" ]
+  defines = [
+    "LIBGTK2UI_IMPLEMENTATION",
+
+    # g_settings_list_schemas is deprecated, but this function is not
+    # available on earlier version that we still need to support.
+    # See build/config/linux/BUILD.gn:gio_config for details.
+    "GLIB_DISABLE_DEPRECATION_WARNINGS",
+  ]
 
   configs += [
     "//build/config/linux:gconf",