[GCM] Updating the list of restricted keys for GCM API messages

chrome/common/extensions/api/gcm.json

 // Copyright 2013 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": "gcm",
     "description": "Use <code>chrome.gcm</code> to enable apps and extensions to send and receive messages through <a href='http://developer.android.com/google/gcm/index.html'>Google Cloud Messaging for Android</a>.",
     "properties": {
       "MAX_MESSAGE_SIZE": {
@@ skipping 59 matching lines @@
                 "optional": true,
                 "description": "Time-to-live of the message in seconds. If it is not possible to send the message wihtin that time an error will be raised. A time-to-live of 0 indicates that the message should be sent immediately or fail if it's not possible. The maximum and a default value of time-to-live is 2419200 seconds (4 weeks)."
               },
               "data": {
                 "type": "object",
                 "properties": {},
                 "additionalProperties": {
                   "type": "string",
                   "minLength": 1
                 },
-                "description": "Message data to send to the server. <code>goog.</code> and <code>google</code> are disallowed as key prefixes. Sum of all key/value pairs should not exceed $(ref:gcm.MAX_MESSAGE_SIZE)."
+                "description": "Message data to send to the server. Case-insensitive <code>goog.</code> and <code>google</code>, as well as case-sensitive <code>collapse_key</code> are disallowed as key prefixes. Sum of all key/value pairs should not exceed $(ref:gcm.MAX_MESSAGE_SIZE)."
               }
             }
           },
           {
             "name": "callback",
             "type": "function",
             "description": "A function called after the message is successfully queued for sending. $(ref:runtime.lastError) should be checked, to ensure a message was sent without problems.",
             "parameters": [
               {
                 "name": "messageId",
@@ skipping 61 matching lines @@
                 "description": "Additional details related to the error, when available."
               }
             },
             "description": "An error that occured while trying to send the message either in Chrome or on the GCM server. Application can retry sending the message with a reasonable backoff and possibly longer time-to-live."
           }
         ]
       }
     ]
   }
 ]