[Approach 3] Pre-allocate IncomigTaskQueue before 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 1129bbffb8272ef42e504bda7cbe9e70afeef80f..e412dea32d36112180dfead2d52e93e9dd8d629a 100644
--- a/chrome/browser/sync/glue/sync_backend_registrar_unittest.cc
+++ b/chrome/browser/sync/glue/sync_backend_registrar_unittest.cc
@@ -336,6 +336,9 @@ TEST_F(SyncBackendRegistrarShutdownTest, BlockingShutdown) {
       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();