Move the device enumerate/open/close work to device thread from IO thread

content/browser/renderer_host/media/media_stream_manager.cc

Index: content/browser/renderer_host/media/media_stream_manager.cc
diff --git a/content/browser/renderer_host/media/media_stream_manager.cc b/content/browser/renderer_host/media/media_stream_manager.cc
index d6b2e60dbaaff16919a76ce2ebce97105ad392d1..676955ef8147ab27f24512b2f95ee0a3a259606d 100644
--- a/content/browser/renderer_host/media/media_stream_manager.cc
+++ b/content/browser/renderer_host/media/media_stream_manager.cc
@@ -20,7 +20,6 @@
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/media_observer.h"
 #include "googleurl/src/gurl.h"
-#include "media/audio/audio_manager.h"
 
 using content::BrowserThread;
 
@@ -116,24 +115,28 @@ struct MediaStreamManager::DeviceRequest {
   StreamDeviceInfoArray video_devices;
 };
 
+// Static function to stop and delete the device thread on blocking pool.
+void ShutdownDeviceThread(base::Thread* thread) {
+  thread->Stop();
+  delete thread;
+}
+
 // static
 MediaStreamManager* MediaStreamManager::GetForResourceContext(
-    content::ResourceContext* resource_context,
-    media::AudioManager* audio_manager) {
+    content::ResourceContext* resource_context) {
   MediaStreamManager* rv = static_cast<MediaStreamManager*>(
       resource_context->GetUserData(kMediaStreamManagerKeyName));
   if (!rv) {
-    rv = new MediaStreamManager(audio_manager);
+    rv = new MediaStreamManager();
     resource_context->SetUserData(kMediaStreamManagerKeyName, rv);
   }
   return rv;
 }
 
-MediaStreamManager::MediaStreamManager(media::AudioManager* audio_manager)
+MediaStreamManager::MediaStreamManager()
     : ALLOW_THIS_IN_INITIALIZER_LIST(
           device_settings_(new MediaStreamDeviceSettings(this))),
-      enumeration_in_progress_(content::NUM_MEDIA_STREAM_DEVICE_TYPES, false),
-      audio_manager_(audio_manager) {
+      enumeration_in_progress_(content::NUM_MEDIA_STREAM_DEVICE_TYPES, false) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 }
 
@@ -143,12 +146,18 @@ MediaStreamManager::~MediaStreamManager() {
     video_capture_manager_->Unregister();
   if (audio_input_device_manager_.get())
     audio_input_device_manager_->Unregister();
+
+  if (device_thread_.get()) {
+    content::BrowserThread::PostBlockingPoolTask(
+        FROM_HERE, base::Bind(&ShutdownDeviceThread, device_thread_.release()));
+  }
 }
 
 VideoCaptureManager* MediaStreamManager::video_capture_manager() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  EnsureDeviceThread();
   if (!video_capture_manager_.get()) {
-    video_capture_manager_ = new VideoCaptureManager();
+    video_capture_manager_ = new VideoCaptureManager(GetMessageLoop());
     video_capture_manager_->Register(this);
   }
   return video_capture_manager_.get();
@@ -156,8 +165,10 @@ VideoCaptureManager* MediaStreamManager::video_capture_manager() {
 
 AudioInputDeviceManager* MediaStreamManager::audio_input_device_manager() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  EnsureDeviceThread();
   if (!audio_input_device_manager_.get()) {
-    audio_input_device_manager_ =  new AudioInputDeviceManager(audio_manager_);
+    audio_input_device_manager_ =  new AudioInputDeviceManager(
+        GetMessageLoop());
     audio_input_device_manager_->Register(this);
   }
   return audio_input_device_manager_.get();
@@ -367,6 +378,15 @@ void MediaStreamManager::StartEnumeration(
   (*label) = request_label;
 }
 
+void MediaStreamManager::EnsureDeviceThread() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  if (device_thread_.get())
+    return;
+
+  device_thread_.reset(new base::Thread("MediaStreamDeviceThread"));
+  CHECK(device_thread_->Start());
+}
+
 void MediaStreamManager::Opened(MediaStreamType stream_type,
                                 int capture_session_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
@@ -613,6 +633,10 @@ void MediaStreamManager::UseFakeDevice() {
   device_settings_->UseFakeUI();
 }
 
+scoped_refptr<base::MessageLoopProxy> MediaStreamManager::GetMessageLoop() {

[scherkus (not reviewing), 2012/06/28 01:24:20]

it still seems unfortunate to expose this for the sake of a unit test
force-quitting the thread

~MediaStreamManager() triggers thread shutdown -- can't we be using the dtor to
post the thread stop to BrowerThread then wait for that message loop to
complete?

+  return device_thread_.get() ? device_thread_->message_loop_proxy() : NULL;
+}
+
 void MediaStreamManager::NotifyObserverDevicesOpened(DeviceRequest* request) {
   content::MediaObserver* media_observer =
       content::GetContentClient()->browser()->GetMediaObserver();