Revert to enumerating all X windows if the Window Manager doesn't support _NE...

chrome/common/gtk_util.cc

 // Copyright (c) 2009 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 "chrome/common/gtk_util.h"
 
 #include <cstdarg>
 #include <gtk/gtk.h>
 #include <gdk/gdkx.h>
 
@@ skipping 198 matching lines @@
   }
 
   return ret;
 }
 
 bool IsScreenComposited() {
   GdkScreen* screen = gdk_screen_get_default();
   return gdk_screen_is_composited(screen) == TRUE;
 }
 
-void EnumerateChildWindows(EnumerateWindowsDelegate* delegate) {
+void EnumerateTopLevelWindows(x11_util::EnumerateWindowsDelegate* delegate) {
   GdkScreen* screen = gdk_screen_get_default();
   GList* stack = gdk_screen_get_window_stack(screen);
-  DCHECK(stack);
+  if (!stack) {
+    // Window Manager doesn't support _NET_CLIENT_LIST_STACKING, so fall back
+    // to old school enumeration of all X windows.
+    x11_util::EnumerateAllWindows(delegate);
+    return;
+  }
 
   for (GList* iter = g_list_last(stack); iter; iter = iter->prev) {
     GdkWindow* window = static_cast<GdkWindow*>(iter->data);
     XID xid = GDK_WINDOW_XID(window);
     if (delegate->ShouldStopIterating(xid))
       break;
   }
 
   g_list_foreach(stack, (GFunc)g_object_unref, NULL);
   g_list_free(stack);
 }
 
 void SetButtonTriggersNavigation(GtkWidget* button) {
   // We handle button activation manually because we want to accept middle mouse
   // clicks.
   g_signal_connect(G_OBJECT(button), "button-press-event",
                    G_CALLBACK(OnMouseButtonPressed), NULL);
   g_signal_connect(G_OBJECT(button), "button-release-event",
                    G_CALLBACK(OnMouseButtonReleased), NULL);
 }
 
 }  // namespace gtk_util