Cleanup WebState and WebStateUserData API

ios/ios_base.gyp

 # Copyright 2013 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.
 {
   'variables': {
     'chromium_code': 1,
    },
   'targets': [
     {
       'target_name': 'ios_consumer_base',
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
-        'consumer/base/supports_user_data.cc',
         'consumer/base/util.mm',
-        'public/consumer/base/supports_user_data.h',
-        'public/consumer/base/util.h',
       ],
     },
   ],
 }