Make GN unit tests single process.

tools/gn/run_all_unittests.cc

 // 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.
 
-#include "base/basictypes.h"
 #include "base/bind.h"
-#include "base/compiler_specific.h"
-#include "base/test/launcher/unit_test_launcher.h"
 #include "base/test/test_suite.h"
 
+// Don't use the multiprocess test harness. This test suite is fast enough and
+// it makes the output more difficult to read.
 int main(int argc, char** argv) {
   base::TestSuite test_suite(argc, argv);
-  return base::LaunchUnitTests(
-      argc, argv, base::Bind(&base::TestSuite::Run,
-      base::Unretained(&test_suite)));
+  return test_suite.Run();
 }