SetCallbackTaskAndThread  177 content/browser/histogram_synchronizer.cc   SetCallbackTaskAndThread(NULL, base::Closure());
SetCallbackTaskAndThread  222 content/browser/histogram_synchronizer.cc   current_synchronizer->SetCallbackTaskAndThread(
SetCallbackTaskAndThread  114 content/browser/histogram_synchronizer.h   void SetCallbackTaskAndThread(base::MessageLoop* callback_thread,