Allow comments in extension config files.

chrome/common/extensions/api/experimental.serial.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.serial",
     "nodoc": true,
     "functions": [
       {
         "name": "open",
         "type": "function",
         "description": "Opens a connection to the given serial port.",
         "parameters": [
@@ skipping 111 matching lines @@
                   }
                 }
               }
             ]
           }
         ]
       }
     ]
   }
 ]