gl_surface_egl: ensure off and on screen surfaces use the same EGLConfig

ui/base/x/x11_util_internal.h

 // Copyright (c) 2011 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_BASE_X_X11_UTIL_INTERNAL_H_
 #define UI_BASE_X_X11_UTIL_INTERNAL_H_
 
 // This file declares utility functions for X11 (Linux only).
 //
 // These functions require the inclusion of the Xlib headers. Since the Xlib
@@ skipping 26 matching lines @@
 UI_BASE_EXPORT void SetX11ErrorHandlers(XErrorHandler error_handler,
                                         XIOErrorHandler io_error_handler);
 
 // NOTE: This function should not be called directly from the
 // X11 Error handler because it queries the server to decode the
 // error message, which may trigger other errors. A suitable workaround
 // is to post a task in the error handler to call this function.
 UI_BASE_EXPORT void LogErrorEventDescription(Display* dpy,
                                              const XErrorEvent& error_event);
 
+// --------------------------------------------------------------------------
+// Selects a Visual with a preference for alpha support. The caller must compare

[Corentin Wallez, 2015/11/22 04:09:01]

nit: The preference for alpha support is only on compositing window managers.

[Julien Isorce Samsung, 2015/11/23 08:28:03]

Acknowledged.

+// depth to 32 to know if the returned visual supports transparency. NULL
+// parameters are allowed to install or query the cached visual and depth.
+UI_BASE_EXPORT void ChooseVisualForWindow(Visual** visual, int* depth);
+
 }  // namespace ui
 
 #endif  // UI_BASE_X_X11_UTIL_INTERNAL_H_