Linux Aura: Use system title bar is now set by preference, not flag.

ui/views/widget/desktop_aura/desktop_root_window_host_x11.cc

 // Copyright (c) 2012 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 "ui/views/widget/desktop_aura/desktop_root_window_host_x11.h"
 
 #include <X11/extensions/shape.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xatom.h>
 #include <X11/Xregion.h>
@@ skipping 588 matching lines @@
 
 bool DesktopWindowTreeHostX11::ShouldUseNativeFrame() const {
   return use_native_frame_;
 }
 
 bool DesktopWindowTreeHostX11::ShouldWindowContentsBeTransparent() const {
   return false;
 }
 
 void DesktopWindowTreeHostX11::FrameTypeChanged() {
+  Widget::FrameType new_type =
+      native_widget_delegate_->AsWidget()->frame_type();
+  SetUseNativeFrame(new_type == Widget::FRAME_TYPE_FORCE_NATIVE);
   // Replace the frame and layout the contents. Even though we don't have a
   // swapable glass frame like on Windows, we still replace the frame because
   // the button assets don't update otherwise.
   native_widget_delegate_->AsWidget()->non_client_view()->UpdateFrame();
 }
 
 NonClientFrameView* DesktopWindowTreeHostX11::CreateNonClientFrameView() {
   return NULL;
 }
 
@@ skipping 983 matching lines @@
   if (linux_ui) {
     ui::NativeTheme* native_theme = linux_ui->GetNativeTheme();
     if (native_theme)
       return native_theme;
   }
 
   return ui::NativeTheme::instance();
 }
 
 }  // namespace views