Linux UI: Never use GTK theme for supervised profiles

chrome/browser/ui/views/chrome_browser_main_extra_parts_views_linux.cc

 // Copyright 2016 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/views/chrome_browser_main_extra_parts_views_linux.h"
 
 #include "base/run_loop.h"
 #include "chrome/browser/chrome_browser_main.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/themes/theme_service.h"
@@ skipping 21 matching lines @@
 
 ui::NativeTheme* GetNativeThemeForWindow(aura::Window* window) {
   if (!window)
     return nullptr;
 
   Profile* profile = GetThemeProfileForWindow(window);
 
   // If using the system (GTK) theme, don't use an Aura NativeTheme at all.
   // NB: ThemeService::UsingSystemTheme() might lag behind this pref. See
   // http://crbug.com/585522
-  if (!profile || profile->GetPrefs()->GetBoolean(prefs::kUsesSystemTheme))
+  if (!profile || (!profile->IsSupervised() &&
+                   profile->GetPrefs()->GetBoolean(prefs::kUsesSystemTheme))) {
     return nullptr;
+  }
 
   // Use a dark theme for incognito browser windows that aren't
   // custom-themed. Otherwise, normal Aura theme.
   if (profile->GetProfileType() == Profile::INCOGNITO_PROFILE &&
       ThemeServiceFactory::GetForProfile(profile)->UsingDefaultTheme() &&
       BrowserView::GetBrowserViewForNativeWindow(window)) {
     return ui::NativeThemeDarkAura::instance();
   }
 
   return ui::NativeTheme::GetInstanceForNativeUi();
@@ skipping 26 matching lines @@
   // because its display::Screen instance depends on it.
   views::LinuxUI::instance()->UpdateDeviceScaleFactor();
   ChromeBrowserMainExtraPartsViews::PreCreateThreads();
   views::X11DesktopHandler::get()->AddObserver(this);
 }
 
 void ChromeBrowserMainExtraPartsViewsLinux::OnWorkspaceChanged(
     const std::string& new_workspace) {
   BrowserList::MoveBrowsersInWorkspaceToFront(new_workspace);
 }