app_mode: Add runtime.onRestartRequired event.

chrome/common/extensions/api/runtime.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": "runtime",
     "documentation_permissions_required": ["runtime"],
     "types": [
       {
@@ skipping 390 matching lines @@
         "parameters": [
           {"name": "message", "type": "any", "description": "The message sent by the calling script."},
           {"name": "sender", "$ref": "MessageSender" },
           {"name": "sendResponse", "type": "function", "description": "Function to call (at most once) when you have a response. The argument should be any JSON-ifiable object. If you have more than one <code>onMessage</code> listener in the same document, then only one may send a response. This function becomes invalid when the event listener returns, unless you return true from the event listener to indicate you wish to send a response asynchronously (this will keep the message channel open to the other end until <code>sendResponse</code> is called)." }
         ],
         "returns": {
           "type": "boolean",
           "optional": "true",
           "description": "Return true from the event listener if you wish to call <code>sendResponse</code> after the event listener returns."
         }
+      },
+      {
+        "name": "onRestartRequired",
+        "type": "function",
+        "description": "Fired when a ChromeOS device running in kiosk mode needs to be restarted. The kiosk app should close all its windows at its earliest convenient time to let the restart to happen. If the app does nothing, a restart will be enforced after a 24-hour grace period has passed.",

[bartfab (slow), 2013/06/17 23:30:59]

Nit: s/ChromeOS/Chrome OS/

Also, how about we document this method in a more generic manner and then
mention that it currently is supported for kiosk mode only? I can see us
supporting this for all session types in the future.

[xiyuan, 2013/06/20 02:17:12]

Done.

+        "parameters": [
+          {
+            "type": "string",
+            "name": "reason",
+            "description": "The reason that the event is being dispatched.",
+            "enum": ["app_update","os_update","periodic"]
+          }
+        ]
       }
-
-
-
     ]
   }
 ]