Improve GN header checker, make //ui pass.

sync/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")
 
 component("sync") {
-  deps = [
+  public_deps = [
     ":sync_core",
     "//sync/protocol",
   ]
-  forward_dependent_configs_from = [ "//sync/protocol" ]
 }
 
 # GYP version: sync/sync.gyp:sync_core
 source_set("sync_core") {
   sources = [
     "api/attachments/attachment.cc",
     "api/attachments/attachment.h",
     "api/attachments/attachment_id.cc",
     "api/attachments/attachment_id.h",
     "api/attachments/attachment_store.cc",
@@ skipping 749 matching lines @@
       "//base",
       "//base/test:test_support",
       "//net:test_support",
       "//testing/gtest",
       ":test_support_sync_testserver",
     ]
   }
 }
 
 #TODO(GYP): Need to port sync_android.gypi and Android test targets.