Deprecate Shift+Alt to switch IME and use Ctrl+Shift+Space instead.

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 15796 matching lines @@
     '7<>CTRL': 'keyboardOverlayActivateTab7',
     '7<>SEARCH': 'keyboardOverlayF7',
     '8<>ALT': 'keyboardOverlayActivateShelfItem8',
     '8<>CTRL': 'keyboardOverlayActivateTab8',
     '8<>SEARCH': 'keyboardOverlayF8',
     '9<>ALT': 'keyboardOverlayActivateLastShelfItem',
     '9<>CTRL': 'keyboardOverlayActivateLastTab',
     '9<>SEARCH': 'keyboardOverlayF9',
     '=<>SEARCH': 'keyboardOverlayF12',
     'ALT<>SEARCH': 'keyboardOverlayToggleCapsLock',
-    'ALT<>SHIFT': 'keyboardOverlayCycleThroughInputMethods',
+    'space<>CTRL<>SHIFT': 'keyboardOverlayCycleThroughInputMethods',

[xiyuan, 2015/11/05 20:33:21]

nit: please keep the list alpha sorted.

[afakhry, 2015/11/05 20:46:42]

Done.

     '[<>ALT': 'keyboardOverlayDockWindowLeft',
     ']<>ALT': 'keyboardOverlayDockWindowRight',
     'a<>CTRL': 'keyboardOverlaySelectAll',
     'arrowkeys<>CTRL': 'keyboardOverlayWordMove',
     'b<>ALT<>SHIFT': 'keyboardOverlayFocusBookmarks',
     'b<>CTRL<>SHIFT': 'keyboardOverlayToggleBookmarkBar',
     'back<>CTRL': 'keyboardOverlayFocusPreviousPane',
     'back<>SEARCH': 'keyboardOverlayF1',
     'backspace': 'keyboardOverlayGoBack',
     'backspace<>ALT': 'keyboardOverlayDelete',
@@ skipping 87 matching lines @@
     'v<>CTRL<>SHIFT': 'keyboardOverlayPasteAsPlainText',
     'vol. down<>SEARCH': 'keyboardOverlayF9',
     'vol. up<>SEARCH': 'keyboardOverlayF10',
     'w<>CTRL': 'keyboardOverlayCloseTab',
     'w<>CTRL<>SHIFT': 'keyboardOverlayCloseWindow',
     'x<>CTRL': 'keyboardOverlayCut',
     'z<>ALT<>CTRL': 'keyboardOverlayToggleChromevoxSpokenFeedback',
     'z<>CTRL': 'keyboardOverlayUndo'
   }
 };