Move app.currentWindowInternal API implementation to extensions

extensions/common/api/schemas.gypi

 # 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.
 
 {
   'sources': [
     '<@(schema_files)',
   ],
   'variables': {
     'chromium_code': 1,
     # TODO: Eliminate these on Android. See crbug.com/305852.
     'android_schema_files': [
       'runtime.json',
     ],
     'main_schema_files': [
+      'app_current_window_internal.idl',
       'app_runtime.idl',
       'app_view_internal.json',
       'app_window.idl',
       'bluetooth.idl',
       'bluetooth_low_energy.idl',
       'bluetooth_private.json',
       'bluetooth_socket.idl',
       'cast_channel.idl',
       'dns.idl',
       'extensions_manifest_types.json',
@@ skipping 29 matching lines @@
         'schema_files': [
           '<@(android_schema_files)',
         ],
       }],
     ],
     'cc_dir': 'extensions/common/api',
     'root_namespace': 'extensions::core_api::%(namespace)s',
     'impl_dir_': 'extensions/browser/api',
   },
 }