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 60 matching lines @@
     io_task_running_ = audio_task_running_ = true;
     audio_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&AudioManagerHelper::UpdateLastAudioThreadTimeTick,
                    base::Unretained(this)));
     monitor_task_runner_->PostTask(
         FROM_HERE, base::Bind(&AudioManagerHelper::RecordAudioThreadStatus,
                               base::Unretained(this)));
   }
 
+  base::SingleThreadTaskRunner* monitor_task_runner() const {
+    return monitor_task_runner_.get();
+  }
   AudioLogFactory* fake_log_factory() { return &fake_log_factory_; }
 
 #if defined(OS_WIN)
   // This should be called before creating an AudioManager in tests to ensure
   // that the creating thread is COM initialized.
   void InitializeCOMForTesting() {
     com_initializer_for_testing_.reset(new base::win::ScopedCOMInitializer());
   }
 #endif
 
@@ skipping 229 matching lines @@
 ScopedAudioManagerPtr AudioManager::CreateForTesting(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
 #if defined(OS_WIN)
   g_helper.Pointer()->InitializeCOMForTesting();
 #endif
   return Create(task_runner, task_runner,
                 g_helper.Pointer()->fake_log_factory());
 }
 
 // static
-void AudioManager::StartHangMonitor(
+void AudioManager::StartHangMonitorIfNeeded(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
+  if (g_helper.Pointer()->monitor_task_runner())
+    return;
+
   DCHECK(AudioManager::Get());
   DCHECK(task_runner);
   DCHECK_NE(task_runner, AudioManager::Get()->GetTaskRunner());
 
   g_helper.Pointer()->StartHangTimer(std::move(task_runner));
 }
 
 // static
 void AudioManager::EnableCrashKeyLoggingForAudioThreadHangs() {
   CHECK(!g_last_created);
@@ skipping 11 matching lines @@
   return g_helper.Pointer()->app_name();
 }
 #endif
 
 // static
 AudioManager* AudioManager::Get() {
   return g_last_created;
 }
 
 }  // namespace media