Take screenshot of active window

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 15877 matching lines @@
     'reload<>SEARCH': 'keyboardOverlayF3',
     'right<>ALT': 'keyboardOverlayGoForward',
     'right<>CTRL': 'keyboardOverlayNextWord',
     'right<>CTRL<>SHIFT': 'keyboardOverlaySelectWordAtATime',
     'right<>SEARCH': 'keyboardOverlayEnd',
     's<>ALT<>SHIFT': 'keyboardOverlayShowStatusMenu',
     's<>CTRL': 'keyboardOverlaySave',
     'space<>CTRL': 'keyboardOverlaySelectPreviousInputMethod',
     'space<>CTRL<>SHIFT': 'keyboardOverlayCycleThroughInputMethods',
     'space<>SHIFT': 'keyboardOverlayScrollUpOnePage',
+    'switch window<>ALT<>CTRL': 'keyboardOverlayScreenshotWindow',

[afakhry, 2016/04/16 01:25:12]

You need to add a corresponding entry for when the top row keys are treated as
function keys.

That is, you need to add the following entry:
'f5<>ALT<>CTRL<>SEARCH': 'keyboardOverlayScreenshotWindow',

here:
https://chromium.googlesource.com/chromium/src/+/b447a543958befb1e16ade0b3e00...

     'switch window<>CTRL': 'keyboardOverlayTakeScreenshot',
     'switch window<>CTRL<>SHIFT': 'keyboardOverlayScreenshotRegion',
     'switch window<>SEARCH': 'keyboardOverlayF5',
     't<>ALT<>CTRL': 'keyboardOverlayNewTerminal',
     't<>ALT<>SHIFT': 'keyboardOverlayFocusToolbar',
     't<>CTRL': 'keyboardOverlayNewTab',
     't<>CTRL<>SHIFT': 'keyboardOverlayReopenLastClosedTab',
     'tab<>ALT': 'keyboardOverlayNextWindow',
     'tab<>ALT<>SHIFT': 'keyboardOverlayPreviousWindow',
     'tab<>CTRL': 'keyboardOverlayActivateNextTab',
     'tab<>CTRL<>SHIFT': 'keyboardOverlayActivatePreviousTab',
     'u<>CTRL': 'keyboardOverlayViewSource',
     'u<>CTRL<>SHIFT': 'keyboardOverlayInputUnicodeCharacters',
     'up<>ALT': 'keyboardOverlayPageUp',
     'up<>ALT<>CTRL': 'keyboardOverlayHome',
     'up<>SEARCH': 'keyboardOverlayPageUp',
     'v<>CTRL': 'keyboardOverlayPaste',
     'v<>CTRL<>SHIFT': 'keyboardOverlayPasteAsPlainText',
     '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'
   }
 };