Adds the legacy KeyboardEvent.keyCode attribute for extension IMEs.

chrome/common/extensions/api/input_ime.json

 // 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.
 
 [
   {
     "namespace": "input.ime",
     "description": "Use the <code>chrome.input.ime</code> API to implement a custom IME for Chrome OS. This allows your extension to handle keystrokes, set the composition, and manage the candidate window.",
     "platforms": ["chromeos"],
     "types": [
       {
         "id": "KeyboardEvent",
         "type": "object",
         "description": "See http://www.w3.org/TR/DOM-Level-3-Events/#events-KeyboardEvent",
         "properties": {
           "type": {"type": "string", "description": "One of keyup or keydown.", "enum": ["keyup", "keydown"]},
           "requestId": {"type": "string", "description": "The ID of the request."},
           "extensionId": {"type": "string", "optional": true, "description": "The extension ID of the sender of this keyevent."},
           "key": {"type": "string", "description": "Value of the key being pressed"},
           "code": {"type": "string", "description": "Value of the physical key being pressed. The value is not affected by current keyboard layout or modifier state."},
+          "keyCode": {"type": "integer", "optional": true, "description": "The deprecated HTML keyCode, which is system- and implementation-dependent numerical code signifying the unmodified identifier associated with the key pressed."},
           "altKey": {"type": "boolean", "optional": true, "description": "Whether or not the ALT key is pressed."},
           "ctrlKey": {"type": "boolean", "optional": true, "description": "Whether or not the CTRL key is pressed."},
           "shiftKey": {"type": "boolean", "optional": true, "description": "Whether or not the SHIFT key is pressed."},
           "capsLock": {"type": "boolean", "optional": true, "description": "Whether or not the CAPS_LOCK is enabled."}
         }
       },
       {
         "id": "InputContext",
         "type": "object",
         "description": "Describes an input Context",
@@ skipping 635 matching lines @@
           {
             "type": "string",
             "name": "engineID",
             "description": "ID of the engine receiving the event"
           }
         ]
       }
     ]
   }
 ]