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);
 
+// --------------------------------------------------------------------------
+// NOTE: This function cache the results and can be called from any thread.

[piman, 2015/11/20 01:44:41]

This is not true, it can only be called from the UI thread, because that the
only place where it's valid to call into the Display.

[Julien Isorce Samsung, 2015/11/20 09:13:56]

Acknowledged. This will also make the function more consistent with the note on
top of the file: "NOTE: these functions ... UI thread"

+// Select a Visual with preference of alpha support. Compare depth to 32 to
+// know if the returned visual support transparency. NULL parameters is allowed.
+UI_BASE_EXPORT void ChooseARGBVisualForWindow(Visual** visual, int* depth);

[piman, 2015/11/20 01:44:41]

How about ChooseVisualForWindow? It's not guaranteed to be ARGB.

[Julien Isorce Samsung, 2015/11/20 09:13:56]

Make sense.

+
 }  // namespace ui
 
 #endif  // UI_BASE_X_X11_UTIL_INTERNAL_H_