Intiialize AudioManager and related class lazily

media/audio/audio_manager.cc

 // Copyright (c) 2012 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/audio/audio_manager.h"
 
 #include <stdint.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 44 matching lines @@
     THREAD_HUNG,
     THREAD_RECOVERED,
     THREAD_MAX = THREAD_RECOVERED
   };
 
   AudioManagerHelper() {}
   ~AudioManagerHelper() override {}
 
   void StartHangTimer(
       scoped_refptr<base::SingleThreadTaskRunner> monitor_task_runner) {
-    CHECK(!monitor_task_runner_);
+    if (monitor_task_runner_)
+      return;
     CHECK(!audio_task_runner_);
     monitor_task_runner_ = std::move(monitor_task_runner);
     audio_task_runner_ = AudioManager::Get()->GetTaskRunner();
     base::PowerMonitor::Get()->AddObserver(this);
 
     io_task_running_ = audio_task_running_ = true;
     audio_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&AudioManagerHelper::UpdateLastAudioThreadTimeTick,
                    base::Unretained(this)));
@@ skipping 277 matching lines @@
   return g_helper.Pointer()->app_name();
 }
 #endif
 
 // static
 AudioManager* AudioManager::Get() {
   return g_last_created;
 }
 
 }  // namespace media