Allow comments in extension config files.

chrome/common/extensions/api/experimental.extension.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": "experimental.extension",
     "events": [
       {
         "name": "onInstalled",
         "type": "function",
         "description": "Fired when the extension is first installed.",
         "parameters": [
         ]
       }
     ]
   }
 ]