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

ui/gfx/x/x11_switches.cc

 // 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.
 
 #include "ui/gfx/x/x11_switches.h"
 
 namespace switches {
 
 #if !defined(OS_CHROMEOS)
+// When enabled, tries to get a transparent X11 visual so that we can have
+// per-pixel alpha in windows.
+//
+// TODO(erg): Remove this switch once we've stabilized the code
+// path. http://crbug.com/369209
+const char kEnableTransparentVisuals[] = "enable-transparent-visuals";
+
+// Color bit depth of the main window created in the browser process and matches
+// XWindowAttributes.depth.
+const char kWindowDepth[] = "window-depth";
+
 // Which X11 display to connect to. Emulates the GTK+ "--display=" command line
 // argument.
 const char kX11Display[] = "display";
 #endif
 
 }  // namespace switches