GTTF: Run perf tests serially

media/base/run_all_perftests.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// 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/bind.h"
 #include "base/command_line.h"
 #include "base/test/launcher/unit_test_launcher.h"
 #include "base/test/test_suite.h"
 #include "build/build_config.h"
 #include "media/base/media.h"
 #include "media/base/media_switches.h"
@@ skipping 27 matching lines @@
   // Run this here instead of main() to ensure an AtExitManager is already
   // present.
   media::InitializeMediaLibraryForTesting();
   CommandLine* cmd_line = CommandLine::ForCurrentProcess();
   cmd_line->AppendSwitch(switches::kEnableMP3StreamParser);
 }
 
 int main(int argc, char** argv) {
   TestSuiteNoAtExit test_suite(argc, argv);
 
-  return base::LaunchUnitTests(
+  // Always run the perf tests serially, to avoid distorting
+  // perf measurements with randomness resulting from running
+  // in parallel.
+  return base::LaunchUnitTestsSerially(
       argc, argv, base::Bind(&TestSuiteNoAtExit::Run,
                              base::Unretained(&test_suite)));
 }