Get 'gn_all' building on iOS

components/policy/core/common/BUILD.gn

 # 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.
 
 import("//build/config/features.gni")
 
 source_set("common") {
-  visibility = [ "//components/policy/*" ]
+  visibility = [
+    "//components/policy/*",
+    "//components/syncable_prefs/*",
+  ]
 
   defines = [ "POLICY_COMPONENT_IMPLEMENTATION" ]
 
   if (enable_configuration_policy) {
     sources = [
       "../../policy_export.h",
       "async_policy_loader.cc",
       "async_policy_loader.h",
       "async_policy_provider.cc",
       "async_policy_provider.h",
@@ skipping 265 matching lines @@
       "//base/test:test_support",
       "//components/policy",
       "//components/policy:policy_component_test_support",
       "//google_apis",
       "//net:test_support",
       "//testing/gmock",
       "//testing/gtest",
     ]
   }
 }