Replace test_support_main by test_main and get rid of test_support_main_threaded_mac

webrtc/test/run_all_unittests.cc

-/*
- *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#include "webrtc/test/test_suite.h"
-
-int main(int argc, char** argv) {
-  webrtc::test::TestSuite test_suite(argc, argv);
-  return test_suite.Run();
-}