Prevent a thread startup race in ScheduleWorkTest which causes a nullptr dereference of a message p…

base/message_loop/message_pump_perftest.cc

 // Copyright 2014 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/bind.h"
 #include "base/format_macros.h"
 #include "base/memory/scoped_vector.h"
 #include "base/strings/stringprintf.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
@@ skipping 52 matching lines @@
   void ScheduleWork(MessageLoop::Type target_type, int num_scheduling_threads) {
 #if defined(OS_ANDROID)
     if (target_type == MessageLoop::TYPE_JAVA) {
       java_thread_.reset(new android::JavaHandlerThread("target"));
       java_thread_->Start();
     } else
 #endif
     {
       target_.reset(new Thread("target"));
       target_->StartWithOptions(Thread::Options(target_type, 0u));
+
+      // Without this, it's possible for the scheduling threads to start and run
+      // before the target thread. In this case, the scheduling threads will
+      // call target_message_loop()->ScheduleWork(), which dereferences the
+      // loop's message pump, which is only created after the target thread has
+      // finished starting.
+      target_->WaitUntilThreadStarted();
     }
 
     ScopedVector<Thread> scheduling_threads;
     scheduling_times_.reset(new base::TimeDelta[num_scheduling_threads]);
     scheduling_thread_times_.reset(new base::TimeDelta[num_scheduling_threads]);
     min_batch_times_.reset(new base::TimeDelta[num_scheduling_threads]);
     max_batch_times_.reset(new base::TimeDelta[num_scheduling_threads]);
 
     for (int i = 0; i < num_scheduling_threads; ++i) {
       scheduling_threads.push_back(new Thread("posting thread"));
@@ skipping 196 matching lines @@
 
 TEST_F(PostTaskTest, TenTasksPerReload) {
   Run(10000, 10);
 }
 
 TEST_F(PostTaskTest, OneHundredTasksPerReload) {
   Run(1000, 100);
 }
 
 }  // namespace base