Try to get rid of all direct references to particular native themes.

ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc

Index: ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
diff --git a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
index 574a2e99d821d8210e6a17e5116dba18040b57f2..4df399879c3dd91fa6224a10fc5a9bce73a0b717 100644
--- a/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
+++ b/ui/views/widget/desktop_aura/desktop_window_tree_host_win.cc
@@ -107,17 +107,7 @@ aura::Window* DesktopWindowTreeHostWin::GetContentWindowForHWND(HWND hwnd) {
 
 // static
 ui::NativeTheme* DesktopWindowTreeHost::GetNativeTheme(aura::Window* window) {
-  // Use NativeThemeWin for windows shown on the desktop, those not on the
-  // desktop come from Ash and get NativeThemeAura.
-  aura::WindowTreeHost* host = window ? window->GetHost() : NULL;
-  if (host) {
-    HWND host_hwnd = host->GetAcceleratedWidget();
-    if (host_hwnd &&
-        DesktopWindowTreeHostWin::GetContentWindowForHWND(host_hwnd)) {
-      return ui::NativeThemeWin::instance();
-    }
-  }
-  return ui::NativeThemeAura::instance();
+  return ui::NativeTheme::GetInstanceForNativeUi();
 }
 
 ////////////////////////////////////////////////////////////////////////////////