Remove obsolete chromeos specific code

chrome/browser/ui/gtk/simple_message_box_gtk.cc

 // Copyright (c) 2012 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/browser/simple_message_box.h"
 
 #include "base/message_loop.h"
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/ui/gtk/gtk_util.h"
 
 namespace {
 
 void SetDialogTitle(GtkWidget* dialog, const string16& title) {
   gtk_window_set_title(GTK_WINDOW(dialog), UTF16ToUTF8(title).c_str());
 
-  // The following code requires the dialog to be realized. However, we host
-  // dialog's content in a Chrome window without really realize the dialog
-  // on ChromeOS. Thus, skip the following code for ChromeOS.
+  // The following code requires the dialog to be realized.
   gtk_widget_realize(dialog);
 
   // Make sure it's big enough to show the title.
   GtkRequisition req;
   gtk_widget_size_request(dialog, &req);
   int width;
   gtk_util::GetWidgetSizeFromCharacters(dialog, title.length(), 0,
                                         &width, NULL);
   // The fudge factor accounts for extra space needed by the frame
   // decorations as well as width differences between average text and the
@@ skipping 50 matching lines @@
                    "response",
                    G_CALLBACK(HandleOnResponseDialog),
                    NULL);
   gtk_util::ShowDialog(dialog);
   // Not gtk_dialog_run as it prevents timers from running in the unit tests.
   MessageLoop::current()->Run();
   return g_dialog_response == GTK_RESPONSE_YES;
 }
 
 }  // namespace browser