[MD settings] show icon when slider controlled by something

ui/webui/resources/cr_elements/cr_slider/compiled_resources2.gyp

 # Copyright 2016 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': 'cr_slider',
       'dependencies': [
+        '<(DEPTH)/ui/webui/resources/cr_elements/policy/compiled_resources2.gyp:cr_policy_pref_behavior',
         '<(DEPTH)/ui/webui/resources/js/compiled_resources2.gyp:assert',
         '<(DEPTH)/third_party/polymer/v1_0/components-chromium/paper-slider/compiled_resources2.gyp:paper-slider-extracted',
       ],
       'includes': ['../../../../../third_party/closure_compiler/compile_js2.gypi'],
     },
   ],
 }