Remove .html extension from links

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</a>.",
+    "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'>Google Cloud Messaging</a>.",
     "properties": {
       "MAX_MESSAGE_SIZE": {
         "value": 4096,
         "description": "The maximum size (in bytes) of all key/value pairs in a message."
       }
     },
     "functions": [
       {
         "name": "register",
         "type": "function",
@@ skipping 151 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."
           }
         ]
       }
     ]
   }
 ]