Add externs for file_manager.

ui/file_manager/gallery/js/compiled_resources.gyp

 # 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': [
     {
       'target_name': 'background',
       'variables': {
         'depends': [
           '../../../webui/resources/js/cr.js',
           '../../../webui/resources/js/cr/event_target.js',
           '../../../webui/resources/js/cr/ui/array_data_model.js',
           '../../../webui/resources/js/load_time_data.js',
           '../../file_manager/common/js/util.js',
           '../../file_manager/common/js/async_util.js',
           '../../file_manager/common/js/volume_manager_common.js',
           '../../file_manager/background/js/volume_manager.js',
           '../../file_manager/common/js/error_util.js',
           '../../file_manager/foreground/js/file_type.js'
         ],
-        'externs': ['<(CLOSURE_DIR)/externs/chrome_send_externs.js'],
+        'externs': [
+          '<(CLOSURE_DIR)/externs/chrome_send_externs.js',
+          '<(CLOSURE_DIR)/externs/chrome_extensions.js',
+          '<(CLOSURE_DIR)/externs/file_manager_private.js',
+        ],
       },
       'includes': [
         '../../../../third_party/closure_compiler/compile_js.gypi'
       ],
     },
     {
       'target_name': 'gallery_scripts',
       'variables': {
         'depends': [
         ],
-        'externs': ['<(CLOSURE_DIR)/externs/chrome_send_externs.js'],
+        'externs': [
+          '<(CLOSURE_DIR)/externs/chrome_send_externs.js',
+          '<(CLOSURE_DIR)/externs/chrome_extensions.js',
+          '<(CLOSURE_DIR)/externs/file_manager_private.js',
+          '<(CLOSURE_DIR)/externs/metrics_private.js',
+        ],
       },
       'includes': [
         '../../../../third_party/closure_compiler/compile_js.gypi'
       ],
     }
   ],
 }