mojo: Fix running view-manager related apptests on X11.

ui/platform_window/x11/x11_window.h

 // Copyright 2014 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.
 
 #ifndef UI_PLATFORM_WINDOW_X11_X11_WINDOW_H_
 #define UI_PLATFORM_WINDOW_X11_X11_WINDOW_H_
 
 #include "ui/events/platform/platform_event_dispatcher.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/x/x11_atom_cache.h"
@@ skipping 48 matching lines @@
   // is the bounds requested using XConfigureWindow, and |confirmed_bounds_| is
   // the bounds the X11 server has set on the window.
   gfx::Rect requested_bounds_;
   gfx::Rect confirmed_bounds_;
 
   bool window_mapped_;
 
   DISALLOW_COPY_AND_ASSIGN(X11Window);
 };
 
+namespace test {
+X11_WINDOW_EXPORT void SetUseOverrideRedirectWindowByDefault(

[msw, 2015/07/16 19:17:50]

Can you add an explanatory comment here? Even after reading
https://tronche.com/gui/x/xlib/window/attributes/override-redirect.html I don't
fully understand the functionality of XSetWindowAttributes::override_redirect
(or the reasoning for setting it).

[sadrul, 2015/07/16 19:57:14]

Added a comment. This is fairly voodoo, and might very well depend on the
particular window-manager/x-server.

+    bool override_redirect);
+}  // namespace test
+
 }  // namespace ui
 
 #endif  // UI_PLATFORM_WINDOW_X11_X11_WINDOW_H_