Fix flaky cast_unittests where threads were being joined incorrectly.

media/cast/test/utility/standalone_cast_environment.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 "media/cast/test/utility/standalone_cast_environment.h"
 
 #include "base/time/default_tick_clock.h"
 
 namespace media {
 namespace cast {
@@ skipping 12 matching lines @@
   CastEnvironment::name##_thread_proxy_ = name##_thread_.message_loop_proxy()
 
   CREATE_TASK_RUNNER(main,
                      base::Thread::Options(base::MessageLoop::TYPE_IO, 0));
   CREATE_TASK_RUNNER(audio, base::Thread::Options());
   CREATE_TASK_RUNNER(video, base::Thread::Options());
 #undef CREATE_TASK_RUNNER
 }
 
 StandaloneCastEnvironment::~StandaloneCastEnvironment() {
-  DCHECK(CalledOnValidThread());
+  CHECK(CalledOnValidThread());
+  CHECK(!main_thread_.IsRunning());
+  CHECK(!audio_thread_.IsRunning());
+  CHECK(!video_thread_.IsRunning());
 }
 
 void StandaloneCastEnvironment::Shutdown() {
-  DCHECK(CalledOnValidThread());
+  CHECK(CalledOnValidThread());
   main_thread_.Stop();
   audio_thread_.Stop();
   video_thread_.Stop();
 }
 
 }  // namespace cast
 }  // namespace media