Cleanup PreferenceMACs on browser_tests startup

content/public/test/test_launcher.cc

 // 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.
 
 #include "content/public/test/test_launcher.h"
 
 #include <stddef.h>
 
 #include <map>
 #include <memory>
@@ skipping 526 matching lines @@
       "--gtest_filter=<your_test_name> flag along with either\n"
       "--single_process (to run the test in one launcher/browser process) or\n"
       "--single-process (to do the above, and also run Chrome in single-"
           "process mode).\n");
 
   base::MessageLoopForIO message_loop;
 #if defined(OS_POSIX)
   base::FileDescriptorWatcher file_descriptor_watcher(&message_loop);
 #endif
 
+  launcher_delegate->PreSharding();
+
   // Allow the |launcher_delegate| to modify |default_jobs|.
   launcher_delegate->AdjustDefaultParallelJobs(&default_jobs);
 
   WrapperTestLauncherDelegate delegate(launcher_delegate);
   base::TestLauncher launcher(&delegate, default_jobs);
   const int result = launcher.Run() ? 0 : 1;
   launcher_delegate->OnDoneRunningTests();
   return result;
 }
 
 TestLauncherDelegate* GetCurrentTestLauncherDelegate() {
   return g_launcher_delegate;
 }
 
 ContentMainParams* GetContentMainParams() {
   return g_params;
 }
 
 }  // namespace content