MD Settings: allow changing to GTK+ theme on Linux

chrome/browser/extensions/api/settings_private/prefs_util.cc

 // Copyright 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.
 
 #include "chrome/browser/extensions/api/settings_private/prefs_util.h"
 
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/chrome_extension_function.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 57 matching lines @@
   (*s_whitelist)["bookmark_bar.show_on_all_tabs"] =
       settings_private::PrefType::PREF_TYPE_BOOLEAN;
   (*s_whitelist)["browser.custom_chrome_frame"] =
       settings_private::PrefType::PREF_TYPE_BOOLEAN;
   (*s_whitelist)["browser.show_home_button"] =
       settings_private::PrefType::PREF_TYPE_BOOLEAN;
 
   // Appearance settings.
   (*s_whitelist)["extensions.theme.id"] =
       settings_private::PrefType::PREF_TYPE_STRING;
+#if defined(OS_LINUX) && !defined(OS_CHROMEOS)
+  (*s_whitelist)["extensions.theme.use_system"] =
+      settings_private::PrefType::PREF_TYPE_BOOLEAN;
+#endif
   (*s_whitelist)["webkit.webprefs.default_fixed_font_size"] =
       settings_private::PrefType::PREF_TYPE_NUMBER;
   (*s_whitelist)["webkit.webprefs.default_font_size"] =
       settings_private::PrefType::PREF_TYPE_NUMBER;
   (*s_whitelist)["webkit.webprefs.minimum_font_size"] =
       settings_private::PrefType::PREF_TYPE_NUMBER;
   (*s_whitelist)["webkit.webprefs.fonts.fixed.Zyyy"] =
       settings_private::PrefType::PREF_TYPE_STRING;
   (*s_whitelist)["webkit.webprefs.fonts.sansserif.Zyyy"] =
       settings_private::PrefType::PREF_TYPE_STRING;
@@ skipping 574 matching lines @@
 
 bool PrefsUtil::IsCrosSetting(const std::string& pref_name) {
 #if defined(OS_CHROMEOS)
   return CrosSettings::Get()->IsCrosSettings(pref_name);
 #else
   return false;
 #endif
 }
 
 }  // namespace extensions