Lazily load extension API schemas

chrome/common/extensions/api/webview.json

 // Copyright (c) 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": "webview",
     "nodoc": true,
-    "dependencies": [ "extension", "tabs" ],
     "types": [
       // TODO(fsamuel): We should be usng tabs.InjectDetails. However, due to a
       // bug in the JSON compiler, we are currently copying-and-pasting this
       // type: https://crbug.com/171726.
       {
         "id": "InjectDetails",
         "type": "object",
         "description": "Details of the script or CSS to inject. Either the code or the file property must be set, but both may not be set at the same time.",
         "properties": {
           "code": {"type": "string", "optional": true, "description": "JavaScript or CSS code to inject."},
@@ skipping 43 matching lines @@
                 "description": "The result of the script in every injected frame."
               }
             ]
           }
         ]
       }
     ]
   }
 ]