Remove UserPolicyDiskCache; it is not used.

chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/chromeos/policy/user_cloud_policy_store_chromeos.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/sequenced_task_runner.h"
 #include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
-#include "chrome/browser/chromeos/policy/user_policy_disk_cache.h"
 #include "chrome/browser/chromeos/policy/user_policy_token_loader.h"
 #include "chromeos/cryptohome/cryptohome_parameters.h"
 #include "chromeos/dbus/cryptohome_client.h"
 #include "chromeos/dbus/session_manager_client.h"
 #include "components/policy/core/common/cloud/cloud_policy_constants.h"
 #include "components/policy/proto/cloud_policy.pb.h"
 #include "components/policy/proto/device_management_local.pb.h"
 #include "google_apis/gaia/gaia_auth_util.h"
 
 namespace em = enterprise_management;
@@ skipping 344 matching lines @@
     validator->ValidateUsername(account_id_.GetUserEmail(), true);
     // The policy loaded from session manager need not be validated using the
     // verification key since it is secure, and since there may be legacy policy
     // data that was stored without a verification key.
     validator->ValidateSignature(cached_policy_key_);
   }
   return validator;
 }
 
 }  // namespace policy