Remove GN GYP generator.

tools/gn/secondary/ipc/BUILD.gn

 # 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.
 
 component("ipc") {
-  external = true
   sources = [
     "file_descriptor_set_posix.cc",
     "file_descriptor_set_posix.h",
     "ipc_channel.cc",
     "ipc_channel.h",
     "ipc_channel_factory.cc",
     "ipc_channel_factory.h",
     "ipc_channel_handle.h",
     "ipc_channel_nacl.cc",
     "ipc_channel_nacl.h",
@@ skipping 56 matching lines @@
   defines = [ "IPC_IMPLEMENTATION" ]
 
   deps = [
     "//base",
     # TODO(viettrungluu): Needed for base/lazy_instance.h, which is suspect.
     "//base/third_party/dynamic_annotations",
   ]
 }
 
 test("ipc_tests") {
-  external = true
   sources = [
     "file_descriptor_set_posix_unittest.cc",
     "ipc_channel_posix_unittest.cc",
     "ipc_channel_unittest.cc",
     "ipc_fuzzing_tests.cc",
     "ipc_message_unittest.cc",
     "ipc_message_utils_unittest.cc",
     "ipc_send_fds_test.cc",
     "ipc_sync_channel_unittest.cc",
     "ipc_sync_message_unittest.cc",
@@ skipping 22 matching lines @@
     ":test_support_ipc",
     "//base",
     "//base:base_i18n",
     "//base/test:run_all_unittests",
     "//base/test:test_support_base",
     "//testing/gtest",
   ]
 }
 
 test("ipc_perftests") {
-  external = true
   sources = [
     "ipc_perftests.cc",
     "ipc_test_base.cc",
     "ipc_test_base.h",
   ]
 
   #if (is_android && gtest_target_type == "shared_library") {
   #  deps += "/testing/android/native_test.gyp:native_testNative_code"
   #}
   #if (is_posix && !is_mac && !is_android) {
   #  # TODO(dmikurube): Kill linux_use_tcmalloc. http://crbug.com/345554
   #  if ((use_allocator!="none" && use_allocator!="see_use_tcmalloc") || (use_allocator=="see_use_tcmalloc" && linux_use_tcmalloc)) {
   #    deps += "//base/allocator"
   #  }
   #}
 
   deps = [
     ":ipc",
     ":test_support_ipc",
     "//base",
     "//base:base_i18n",
     "//base/test:test_support_base",
     "//base/test:test_support_perf",
     "//testing/gtest",
   ]
 }
 
 static_library("test_support_ipc") {
-  external = true
   sources = [
     "ipc_multiprocess_test.cc",
     "ipc_multiprocess_test.h",
     "ipc_test_sink.cc",
     "ipc_test_sink.h",
   ]
   deps = [
     ":ipc",
     "//base",
     "//testing/gtest",
   ]
 }