MD Settings: don't allow supervised users to switch to GTK+ theme

chrome/browser/ui/webui/settings/appearance_handler.cc

 // 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.
 
 #include "chrome/browser/ui/webui/settings/appearance_handler.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/values.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 35 matching lines @@
                  base::Unretained(this)));
 #endif
 }
 
 void AppearanceHandler::HandleUseDefaultTheme(const base::ListValue* args) {
   ThemeServiceFactory::GetForProfile(profile_)->UseDefaultTheme();
 }
 
 #if defined(OS_LINUX) && !defined(OS_CHROMEOS)
 void AppearanceHandler::HandleUseSystemTheme(const base::ListValue* args) {
-  ThemeServiceFactory::GetForProfile(profile_)->UseSystemTheme();
+  if (profile_->IsSupervised())
+    NOTREACHED();
+  else
+    ThemeServiceFactory::GetForProfile(profile_)->UseSystemTheme();
 }
 #endif
 
 #if defined(OS_CHROMEOS)
 void AppearanceHandler::HandleOpenWallpaperManager(
     const base::ListValue* /*args*/) {
   ash::WmShell::Get()->wallpaper_delegate()->OpenSetWallpaperPage();
 }
 #endif
 
 }  // namespace settings