Enable to show the keyboard overlay by shortcut key.

chrome/app/chrome_command_ids.h

 // Copyright (c) 2010 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.
 
 // This file lists all the command IDs understood by e.g. the browser.
 // It is used by Windows RC files, Mac NIB files, and other platforms too.
 
 #define IDC_View                        4000
 #define IDC_ViewHost                    4001
 #define IDC_Plugin                      4002
@@ skipping 155 matching lines @@
 #define IDC_VIEW_PASSWORDS              40017
 #define IDC_ABOUT                       40018
 #define IDC_HELP_PAGE                   40019
 #define IDC_SHOW_APP_MENU               40020
 #define IDC_MANAGE_EXTENSIONS           40022
 #define IDC_AUTOFILL_DEFAULT            40023
 #define IDC_DEV_TOOLS_INSPECT           40025
 #define IDC_UPGRADE_DIALOG              40026
 #define IDC_VIEW_INCOMPATIBILITIES      40027
 #define IDC_VIEW_BACKGROUND_PAGES       40028
+#define IDC_SHOW_KEYBOARD_OVERLAY       40029
 
 // Spell-check
 // Insert any additional suggestions before _LAST; these have to be consecutive.
 #define IDC_SPELLCHECK_SUGGESTION_0     41000
 #define IDC_SPELLCHECK_SUGGESTION_1     41001
 #define IDC_SPELLCHECK_SUGGESTION_2     41002
 #define IDC_SPELLCHECK_SUGGESTION_3     41003
 #define IDC_SPELLCHECK_SUGGESTION_4     41004
 #define IDC_SPELLCHECK_SUGGESTION_LAST  IDC_SPELLCHECK_SUGGESTION_4
 #define IDC_SPELLCHECK_MENU             41005
@@ skipping 81 matching lines @@
 // Frame items.
 #define IDC_CONTENT_CONTEXT_RELOADFRAME 50160
 #define IDC_CONTENT_CONTEXT_OPENFRAMENEWTAB 50161
 #define IDC_CONTENT_CONTEXT_OPENFRAMENEWWINDOW 50162
 #define IDC_CONTENT_CONTEXT_OPENFRAMEOFFTHERECORD 50163
 #define IDC_CONTENT_CONTEXT_VIEWFRAMESOURCE 50164
 #define IDC_CONTENT_CONTEXT_VIEWFRAMEINFO 50165
 // Search items.
 #define IDC_CONTENT_CONTEXT_GOTOURL 50170
 #define IDC_CONTENT_CONTEXT_SEARCHWEBFOR 50171