Intiialize AudioManager and related class lazily

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index b53236dd828b8a7eaeffe2e4de7ee55406f8a46b..cef8429785e40b79ee44d37e2fffcd79657e1cb4 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -1228,11 +1228,12 @@ int BrowserMainLoop::BrowserThreadsStarted() {
       nullptr);
 #endif
 
+#if !defined(OS_ANDROID)
   {
-    TRACE_EVENT0("startup", "BrowserThreadsStarted::Subsystem:AudioMan");
-    CreateAudioManager();
+    TRACE_EVENT0("startup", "BrowserThreadsStarted::InitMediaComponents");

[no sievers, 2016/06/20 23:50:58]

nit: maybe move the trace event into the function where we actually init?

+    InitializeMediaComponentsIfNeeded();
   }
-
+#endif
   {
     TRACE_EVENT0("startup", "BrowserThreadsStarted::Subsystem:MidiManager");
     midi_manager_.reset(media::midi::MidiManager::Create());
@@ -1258,20 +1259,6 @@ int BrowserMainLoop::BrowserThreadsStarted() {
     resource_dispatcher_host_.reset(new ResourceDispatcherHostImpl());
   }
 
-  // MediaStreamManager needs the IO thread to be created.
-  {
-    TRACE_EVENT0("startup",
-      "BrowserMainLoop::BrowserThreadsStarted:InitMediaStreamManager");
-    media_stream_manager_.reset(new MediaStreamManager(audio_manager_.get()));
-  }
-
-  {
-    TRACE_EVENT0("startup",
-      "BrowserMainLoop::BrowserThreadsStarted:InitSpeechRecognition");
-    speech_recognition_manager_.reset(new SpeechRecognitionManagerImpl(
-        audio_manager_.get(), media_stream_manager_.get()));
-  }
-
   {
     TRACE_EVENT0(
         "startup",
@@ -1466,9 +1453,12 @@ void BrowserMainLoop::EndStartupTracing() {
           base::Bind(OnStoppedStartupTracing, startup_trace_file_)));
 }
 
-void BrowserMainLoop::CreateAudioManager() {
+void BrowserMainLoop::InitializeMediaComponentsIfNeeded() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
+  if (audio_manager_)
+    return;
+
   DCHECK(!audio_thread_);
-  DCHECK(!audio_manager_);
 
   bool use_hang_monitor = true;
   audio_manager_ = GetContentClient()->browser()->CreateAudioManager(
@@ -1501,6 +1491,11 @@ void BrowserMainLoop::CreateAudioManager() {
 
   if (use_hang_monitor)
     media::AudioManager::StartHangMonitor(io_thread_->task_runner());
+
+  // MediaStreamManager needs the IO thread to be created.
+  media_stream_manager_.reset(new MediaStreamManager(audio_manager_.get()));
+  speech_recognition_manager_.reset(new SpeechRecognitionManagerImpl(
+      audio_manager_.get(), media_stream_manager_.get()));
 }
 
 }  // namespace content