[ChromeOS] Add device wallpaper policy handler to ensure the policy display correctly in chrome://p…

chrome/browser/policy/configuration_policy_handler_list_factory.cc

 // 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.
 
 #include "chrome/browser/policy/configuration_policy_handler_list_factory.h"
 
 #include <limits.h>
 #include <stddef.h>
 
 #include <utility>
@@ skipping 931 matching lines @@
   handlers->AddHandler(base::MakeUnique<LegacyPoliciesDeprecatingPolicyHandler>(
       std::move(power_management_idle_legacy_policies),
       base::WrapUnique(
           new PowerManagementIdleSettingsPolicyHandler(chrome_schema))));
   handlers->AddHandler(base::MakeUnique<LegacyPoliciesDeprecatingPolicyHandler>(
       std::move(screen_lock_legacy_policies),
       base::WrapUnique(new ScreenLockDelayPolicyHandler(chrome_schema))));
   handlers->AddHandler(
       base::MakeUnique<ExternalDataPolicyHandler>(key::kUserAvatarImage));
   handlers->AddHandler(
+      base::MakeUnique<ExternalDataPolicyHandler>(key::kDeviceWallpaperImage));
+  handlers->AddHandler(
       base::MakeUnique<ExternalDataPolicyHandler>(key::kWallpaperImage));
   handlers->AddHandler(base::WrapUnique(new SimpleSchemaValidatingPolicyHandler(
       key::kSessionLocales, NULL, chrome_schema, SCHEMA_STRICT,
       SimpleSchemaValidatingPolicyHandler::RECOMMENDED_ALLOWED,
       SimpleSchemaValidatingPolicyHandler::MANDATORY_PROHIBITED)));
   handlers->AddHandler(
       base::MakeUnique<chromeos::KeyPermissionsPolicyHandler>(chrome_schema));
   handlers->AddHandler(base::WrapUnique(new DefaultGeolocationPolicyHandler()));
 #endif  // defined(OS_CHROMEOS)
 
 #if BUILDFLAG(ENABLE_PLUGINS)
   handlers->AddHandler(base::MakeUnique<PluginPolicyHandler>());
 #endif  // BUILDFLAG(ENABLE_PLUGINS)
 
   return handlers;
 }
 
 }  // namespace policy