Add the shortcut to toggle high contrast mode to the keyboard overlay

chrome/browser/resources/chromeos/keyboard_overlay_data.js

 // 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.
 
 // This is a generated file but may contain local modifications. See
 // src/tools/gen_keyboard_overlay_data/gen_keyboard_overlay_data.py --help
 
 var keyboardOverlayData = {
   'inputMethodIdToOverlayId': {
     'xkb:be::fra': 'fr',
@@ skipping 15852 matching lines @@
     'f9<>SEARCH': 'keyboardOverlayVolDownKeyLabel',
     'f10<>SEARCH': 'keyboardOverlayVolUpKeyLabel',
     'f10<>SHIFT': 'keyboardOverlayContextMenu',
     'forward<>CTRL': 'keyboardOverlayFocusNextPane',
     'forward<>SEARCH': 'keyboardOverlayF2',
     'full screen<>ALT': 'keyboardOverlaySwapPrimaryMonitor',
     'full screen<>CTRL': 'keyboardOverlayMirrorMonitors',
     'full screen<>SEARCH': 'keyboardOverlayF4',
     'g<>CTRL': 'keyboardOverlayFindTextAgain',
     'g<>CTRL<>SHIFT': 'keyboardOverlayFindPreviousText',
+    'h<>ALT<>CTRL': 'keyboardOverlayToggleHighContrastMode',
     'h<>CTRL': 'keyboardOverlayHistory',
     'i<>ALT<>SHIFT': 'keyboardOverlayReportIssue',
     'i<>CTRL<>SHIFT': 'keyboardOverlayDeveloperTools',
     'j<>CTRL': 'keyboardOverlayDownloads',
     'j<>CTRL<>SHIFT': 'keyboardOverlayJavascriptConsole',
     'k<>CTRL': 'keyboardOverlayFocusAddressBarInSearchMode',
     'l<>ALT<>SHIFT': 'keyboardOverlayFocusShelf',
     'l<>CTRL': 'keyboardOverlayFocusAddressBar',
     'l<>SEARCH': 'keyboardOverlayLockScreen',
     'l<>SEARCH<>SHIFT': 'keyboardOverlaySuspend',
@@ skipping 47 matching lines @@
     'vol. down<>SEARCH': 'keyboardOverlayF9',
     'vol. up<>SEARCH': 'keyboardOverlayF10',
     'vol. up<>SEARCH<>SHIFT': 'keyboardOverlayContextMenu',
     'w<>CTRL': 'keyboardOverlayCloseTab',
     'w<>CTRL<>SHIFT': 'keyboardOverlayCloseWindow',
     'x<>CTRL': 'keyboardOverlayCut',
     'z<>ALT<>CTRL': 'keyboardOverlayToggleChromevoxSpokenFeedback',
     'z<>CTRL': 'keyboardOverlayUndo'
   }
 };