Intiialize AudioManager and related class lazily

content/browser/browser_main_loop.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 "content/browser/browser_main_loop.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 1210 matching lines @@
   // BrowserProcessSubThread::IOThreadPreCleanUp).
   base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
       BrowserGpuMemoryBufferManager::current(), "BrowserGpuMemoryBufferManager",
       io_thread_->task_runner());
 #if defined(OS_ANDROID)
   base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
       tracing::GraphicsMemoryDumpProvider::GetInstance(), "AndroidGraphics",
       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());
   }
 
 #if defined(OS_WIN)
   system_message_window_.reset(new media::SystemMessageWindowWin);
 #elif defined(OS_LINUX) && defined(USE_UDEV)
   device_monitor_linux_.reset(
       new media::DeviceMonitorLinux(io_thread_->task_runner()));
 #elif defined(OS_MACOSX)
   device_monitor_mac_.reset(new media::DeviceMonitorMac());
 #endif
 
 #if defined(OS_WIN)
   UMA_HISTOGRAM_BOOLEAN("Windows.Win32kRendererLockdown",
                         IsWin32kRendererLockdownEnabled());
 #endif
   // RDH needs the IO thread to be created
   {
     TRACE_EVENT0("startup",
       "BrowserMainLoop::BrowserThreadsStarted:InitResourceDispatcherHost");
     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",
         "BrowserMainLoop::BrowserThreadsStarted::InitUserInputMonitor");
     user_input_monitor_ = media::UserInputMonitor::Create(
         io_thread_->task_runner(), main_thread_->task_runner());
   }
 
   {
     TRACE_EVENT0("startup",
@@ skipping 174 matching lines @@
 void BrowserMainLoop::EndStartupTracing() {
   DCHECK(is_tracing_startup_for_duration_);
 
   is_tracing_startup_for_duration_ = false;
   TracingController::GetInstance()->StopTracing(
       TracingController::CreateFileSink(
           startup_trace_file_,
           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(
       MediaInternals::GetInstance());
   if (!audio_manager_) {
     audio_thread_.reset(new base::Thread("AudioThread"));
 #if defined(OS_WIN)
     audio_thread_->init_com_with_mta(true);
 #endif  // defined(OS_WIN)
     CHECK(audio_thread_->Start());
@@ skipping 12 matching lines @@
     scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner =
         audio_thread_->task_runner();
     audio_manager_ = media::AudioManager::Create(std::move(audio_task_runner),
                                                  std::move(worker_task_runner),
                                                  MediaInternals::GetInstance());
   }
   CHECK(audio_manager_);
 
   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