Add support for app_shell-only extension APIs

extensions/shell/common/api/api.gyp

-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Copyright 2014 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.
 
 {
   'targets': [
     {
-      # GN version: //chrome/common/extensions/api:api
-      'target_name': 'chrome_api',
+      'target_name': 'shell_api',
       'type': 'static_library',
-      'sources': [
-        '<@(schema_files)',
-      ],
       # TODO(jschuh): http://crbug.com/167187 size_t -> int
       'msvs_disabled_warnings': [ 4267 ],
       'includes': [
         '../../../../build/json_schema_bundle_compile.gypi',
         '../../../../build/json_schema_compile.gypi',
         'schemas.gypi',
       ],
-      'dependencies': [
-        '<@(schema_dependencies)',
-      ],
     },
   ],
 }