Get Polymer externs from closure/github (instead of Polymer/bower)

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': [
           '../../../../third_party/jstemplate/compiled_resources.gyp:jstemplate',
@@ skipping 121 matching lines @@
           './ribbon.js',
           './slide_mode.js',
           './thumbnail_mode.js',
         ],
         'externs': [
           '<(EXTERNS_DIR)/chrome_extensions.js',
           '<(EXTERNS_DIR)/chrome_send.js',
           '<(EXTERNS_DIR)/file_manager_private.js',
           '<(EXTERNS_DIR)/metrics_private.js',
           '../../../../third_party/analytics/externs.js',
-          '../../../../third_party/polymer/v1_0/components-chromium/polymer-externs/polymer.externs.js',
+          '../../../../third_party/closure_compiler/externs/polymer-1.0.js',
           '../../externs/chrome_test.js',
           '../../externs/es6_workaround.js',
           '../../externs/exif_entry.js',
           '../../externs/files_elements.js',
           '../../externs/gallery_foreground.js',
           '../../externs/paper_elements.js',
           '../../externs/platform.js',
           '../../externs/webview_tag.js',
         ],
       },
       'includes': [
         '../../compile_js.gypi',
       ],
     }
   ],
 }