Revert of Lazily initialize MessageLoop for faster thread startup

chrome/browser/sync/glue/sync_backend_registrar_unittest.cc

Index: chrome/browser/sync/glue/sync_backend_registrar_unittest.cc
diff --git a/chrome/browser/sync/glue/sync_backend_registrar_unittest.cc b/chrome/browser/sync/glue/sync_backend_registrar_unittest.cc
index 34adb95c58be3837c71f0c6b9987fdf1040df44b..3db65e9aa8506800906545295e371b71596ff562 100644
--- a/chrome/browser/sync/glue/sync_backend_registrar_unittest.cc
+++ b/chrome/browser/sync/glue/sync_backend_registrar_unittest.cc
@@ -336,9 +336,6 @@
       base::Bind(&SyncBackendRegistrar::Shutdown,
                  base::Unretained(registrar.release())));
 
-  // Make sure the thread starts running.
-  sync_thread->WaitUntilThreadStarted();
-
   // The test verifies that the sync thread doesn't block because
   // of the blocked DB thread and can finish the shutdown.
   sync_thread->message_loop()->RunUntilIdle();