memory-infra: Fix MemoryDumpScheduler test.

base/trace_event/memory_dump_scheduler_unittest.cc

 // Copyright 2017 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/trace_event/memory_dump_scheduler.h"
 
 #include <memory>
 
 #include "base/bind.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 167 matching lines @@
 
   scheduler_->Start(config, bg_thread_->task_runner());
   evt.Wait();
   scheduler_->Stop();
   bg_thread_->Stop();
 
   bg_thread_.reset(new Thread("MemoryDumpSchedulerTest Thread 2"));
   bg_thread_->Start();
   evt.Reset();
   expected_task_runner = bg_thread_->task_runner();
-  scheduler_->Start(config, bg_thread_->task_runner());
   EXPECT_CALL(on_tick_, OnTick(_)).Times(kTicks - 1);
   EXPECT_CALL(on_tick_, OnTick(_))
       .WillRepeatedly(
           Invoke([&evt, expected_task_runner](MemoryDumpLevelOfDetail) {
             EXPECT_TRUE(expected_task_runner->RunsTasksOnCurrentThread());
             evt.Signal();
           }));
+  scheduler_->Start(config, bg_thread_->task_runner());
   evt.Wait();
   scheduler_->Stop();
 }
 
 }  // namespace trace_event
 }  // namespace base