Lazily load extension API schemas

chrome/common/extensions/api/context_menus.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": "contextMenus",
-    "dependencies": [ "tabs" ],
     "types": [
       {
         "id": "OnClickData",
         "type": "object",
         "description": "Information sent when a context menu item is clicked.",
         "properties": {
           "menuItemId": {
             "choices": [
               { "type": "integer" },
               { "type": "string" }
@@ skipping 285 matching lines @@
             "name": "tab",
             "$ref": "tabs.Tab",
             "description": "The details of the tab where the click took place. If the click did not take place in a tab, this parameter will be missing.",
             "optional": true
           }
         ]
       }
     ]
   }
 ]