GN: Remove duplicate entries from sources lists

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 = [
     ":sync_core",
     "//sync/protocol",
@@ skipping 156 matching lines @@
     "internal_api/public/attachments/attachment_uploader_impl.h",
     "internal_api/public/attachments/fake_attachment_downloader.h",
     "internal_api/public/attachments/fake_attachment_uploader.h",
     "internal_api/public/base/attachment_id_proto.cc",
     "internal_api/public/base/attachment_id_proto.h",
     "internal_api/public/base/cancelation_observer.cc",
     "internal_api/public/base/cancelation_observer.h",
     "internal_api/public/base/cancelation_signal.cc",
     "internal_api/public/base/cancelation_signal.h",
     "internal_api/public/base/enum_set.h",
-    "internal_api/public/base/enum_set.h",
     "internal_api/public/base/invalidation_interface.cc",
     "internal_api/public/base/invalidation_interface.h",
     "internal_api/public/base/model_type.h",
     "internal_api/public/base_node.h",
     "internal_api/public/base/node_ordinal.cc",
     "internal_api/public/base/node_ordinal.h",
     "internal_api/public/base/ordinal.h",
     "internal_api/public/base/progress_marker_map.cc",
     "internal_api/public/base/progress_marker_map.h",
     "internal_api/public/base_transaction.h",
@@ skipping 581 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.