Make tooltips toplevel windows on Linux

ui/views/widget/desktop_aura/desktop_window_tree_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_window_tree_host_x11.h"
 
 #include <X11/extensions/shape.h>
 #include <X11/extensions/XInput2.h>
 #include <X11/Xatom.h>
 #include <X11/Xregion.h>
@@ skipping 920 matching lines @@
   memset(&swa, 0, sizeof(swa));
   swa.background_pixmap = None;
 
   ::Atom window_type;
   switch (params.type) {
     case Widget::InitParams::TYPE_MENU:
       swa.override_redirect = True;
       window_type = atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE_MENU");
       break;
     case Widget::InitParams::TYPE_TOOLTIP:
+      swa.override_redirect = True;
       window_type = atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE_TOOLTIP");
       break;
     case Widget::InitParams::TYPE_POPUP:
       swa.override_redirect = True;
       window_type = atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE_NOTIFICATION");
       break;
     case Widget::InitParams::TYPE_DRAG:
       swa.override_redirect = True;
       window_type = atom_cache_.GetAtom("_NET_WM_WINDOW_TYPE_DND");
       break;
@@ skipping 726 matching lines @@
   if (linux_ui) {
     ui::NativeTheme* native_theme = linux_ui->GetNativeTheme(window);
     if (native_theme)
       return native_theme;
   }
 
   return ui::NativeTheme::instance();
 }
 
 }  // namespace views