Revert 150491 - refactor EnumerateDevices to make it a persistent request.

After the requester calls EnumerateDevices, it should expect new device list as initial response and whenever devices are changed.
A new method StopEnumerateDevices is also added to allow the request to stop device enumeration.

It also includes corresponding change in Pepper since EnumerateDevices contract is changed (http://codereview.chromium.org/10837064/).
This patch keeps current Pepper API, while using the new API of EnumerateDevices from MediaStreamDispatcher. 
Pepper calls StopEnumerateDevices when it receives the first enumerated result. 

A new Pepper API will be created in a separate patch to make EnumerateDevices persistent. 

BUG=137799
Review URL: https://chromiumcodereview.appspot.com/10830063

BUG=141367

TBR=wjia@chromium.org
Review URL: https://chromiumcodereview.appspot.com/10834232

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@150593 0039d316-1c4b-4281-b951-d872f2087c98

17 files changed, 113 insertions, 508 deletions

diff --git a/content/browser/renderer_host/media/media_stream_dispatcher_host.cc b/content/browser/renderer_host/media/media_stream_dispatcher_host.cc
index 1f6eb43..fb817b9 100644
--- a/content/browser/renderer_host/media/media_stream_dispatcher_host.cc
+++ b/content/browser/renderer_host/media/media_stream_dispatcher_host.cc
@@ -100,9 +100,10 @@ void MediaStreamDispatcherHost::DevicesEnumerated(
   StreamMap::iterator it = streams_.find(label);
   DCHECK(it != streams_.end());
   StreamRequest request = it->second;
+  streams_.erase(it);
 
   Send(new MediaStreamMsg_DevicesEnumerated(
-      request.render_view_id, request.page_request_id, label, devices));
+      request.render_view_id, request.page_request_id, devices));
 }
 
 void MediaStreamDispatcherHost::DeviceOpened(
@@ -195,6 +196,7 @@ void MediaStreamDispatcherHost::OnStopGeneratedStream(
            << ", {label = " << label <<  "})";
 
   StreamMap::iterator it = streams_.find(label);
+  DCHECK(it != streams_.end());
   GetManager()->StopGeneratedStream(label);
   streams_.erase(it);
 }
diff --git a/content/browser/renderer_host/media/media_stream_manager.cc b/content/browser/renderer_host/media/media_stream_manager.cc
index b41b244..1329b97 100644
--- a/content/browser/renderer_host/media/media_stream_manager.cc
+++ b/content/browser/renderer_host/media/media_stream_manager.cc
@@ -47,10 +47,14 @@ static std::string RandomLabel() {
 // Helper to verify if a media stream type is part of options or not.
 static bool Requested(const StreamOptions& options,
                       MediaStreamType stream_type) {
-  return (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE &&
-          options.video) ||
-         (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE &&
-          options.audio);
+  if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE &&
+      options.video) {
+    return true;
+  } else if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE &&
+             options.audio) {
+    return true;
+  }
+  return false;
 }
 
 DeviceThread::DeviceThread(const char* name)
@@ -74,24 +78,24 @@ void DeviceThread::CleanUp() {
 // TODO(xians): Merge DeviceRequest with MediaStreamRequest.
 struct MediaStreamManager::DeviceRequest {
   enum RequestState {
-    STATE_NOT_REQUESTED = 0,
-    STATE_REQUESTED,
-    STATE_PENDING_APPROVAL,
-    STATE_OPENING,
-    STATE_DONE,
-    STATE_ERROR
+    kNotRequested = 0,
+    kRequested,
+    kPendingApproval,
+    kOpening,
+    kDone,
+    kError
   };
 
   enum RequestType {
-    GENERATE_STREAM = 0,
-    ENUMERATE_DEVICES,
-    OPEN_DEVICE
+    kGenerateStream = 0,
+    kEnumerateDevices,
+    kOpenDevice
   };
 
   DeviceRequest()
       : requester(NULL),
-        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, STATE_NOT_REQUESTED),
-        type(GENERATE_STREAM),
+        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, kNotRequested),
+        type(kGenerateStream),
         render_process_id(-1),
         render_view_id(-1) {
     options.audio = false;
@@ -105,8 +109,8 @@ struct MediaStreamManager::DeviceRequest {
                 const GURL& request_security_origin)
       : requester(requester),
         options(request_options),
-        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, STATE_NOT_REQUESTED),
-        type(GENERATE_STREAM),
+        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, kNotRequested),
+        type(kGenerateStream),
         render_process_id(render_process_id),
         render_view_id(render_view_id),
         security_origin(request_security_origin) {
@@ -127,13 +131,6 @@ struct MediaStreamManager::DeviceRequest {
   StreamDeviceInfoArray video_devices;
 };
 
-MediaStreamManager::EnumerationCache::EnumerationCache()
-    : valid(false) {
-}
-
-MediaStreamManager::EnumerationCache::~EnumerationCache() {
-}
-
 MediaStreamManager::MediaStreamManager(
     AudioInputDeviceManager* audio_input_device_manager,
     VideoCaptureManager* video_capture_manager)
@@ -141,10 +138,8 @@ MediaStreamManager::MediaStreamManager(
           device_settings_(new MediaStreamDeviceSettings(this))),
       audio_input_device_manager_(audio_input_device_manager),
       video_capture_manager_(video_capture_manager),
-      monitoring_started_(false),
+      enumeration_in_progress_(content::NUM_MEDIA_STREAM_DEVICE_TYPES, false),
       io_loop_(NULL) {
-  memset(active_enumeration_ref_count_, 0,
-         sizeof(active_enumeration_ref_count_));
 }
 
 MediaStreamManager::~MediaStreamManager() {
@@ -181,17 +176,6 @@ void MediaStreamManager::GenerateStream(MediaStreamRequester* requester,
                             render_view_id,
                             security_origin);
   StartEnumeration(&new_request, label);
-
-  // Get user confirmation to use capture devices.
-  // Need to make an asynchronous call to make sure the |requester| gets the
-  // |label| before it would receive any event.
-  BrowserThread::PostTask(BrowserThread::IO,
-      FROM_HERE,
-      base::Bind(&MediaStreamDeviceSettings::RequestCaptureDeviceUsage,
-                 base::Unretained(device_settings_.get()),
-                 *label, render_process_id,
-                 render_view_id, options,
-                 security_origin));
 }
 
 void MediaStreamManager::CancelRequests(MediaStreamRequester* requester) {
@@ -203,7 +187,7 @@ void MediaStreamManager::CancelRequests(MediaStreamRequester* requester) {
       // opened -> close them.
       DeviceRequest* request = &(it->second);
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE] ==
-          DeviceRequest::STATE_OPENING) {
+          DeviceRequest::kOpening) {
         for (StreamDeviceInfoArray::iterator it =
              request->audio_devices.begin(); it != request->audio_devices.end();
              ++it) {
@@ -211,7 +195,7 @@ void MediaStreamManager::CancelRequests(MediaStreamRequester* requester) {
         }
       }
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE] ==
-          DeviceRequest::STATE_OPENING) {
+          DeviceRequest::kOpening) {
         for (StreamDeviceInfoArray::iterator it =
              request->video_devices.begin(); it != request->video_devices.end();
              ++it) {
@@ -234,7 +218,7 @@ void MediaStreamManager::CancelGenerateStream(const std::string& label) {
     if (!RequestDone(it->second)) {
       DeviceRequest* request = &(it->second);
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE] ==
-          DeviceRequest::STATE_OPENING) {
+          DeviceRequest::kOpening) {
         for (StreamDeviceInfoArray::iterator it =
              request->audio_devices.begin(); it != request->audio_devices.end();
              ++it) {
@@ -242,7 +226,7 @@ void MediaStreamManager::CancelGenerateStream(const std::string& label) {
         }
       }
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE] ==
-          DeviceRequest::STATE_OPENING) {
+          DeviceRequest::kOpening) {
         for (StreamDeviceInfoArray::iterator it =
              request->video_devices.begin(); it != request->video_devices.end();
              ++it) {
@@ -262,10 +246,6 @@ void MediaStreamManager::StopGeneratedStream(const std::string& label) {
   // Find the request and close all open devices for the request.
   DeviceRequests::iterator it = requests_.find(label);
   if (it != requests_.end()) {
-    if (it->second.type == DeviceRequest::ENUMERATE_DEVICES) {
-      StopEnumerateDevices(label);
-      return;
-    }
     for (StreamDeviceInfoArray::iterator audio_it =
          it->second.audio_devices.begin();
          audio_it != it->second.audio_devices.end(); ++audio_it) {
@@ -276,10 +256,11 @@ void MediaStreamManager::StopGeneratedStream(const std::string& label) {
          video_it != it->second.video_devices.end(); ++video_it) {
       video_capture_manager()->Close(video_it->session_id);
     }
-    if (it->second.type == DeviceRequest::GENERATE_STREAM) {
+    if (it->second.type == DeviceRequest::kGenerateStream) {
       NotifyObserverDevicesClosed(&(it->second));
     }
     requests_.erase(it);
+    return;
   }
 }
 
@@ -291,53 +272,21 @@ void MediaStreamManager::EnumerateDevices(
     const GURL& security_origin,
     std::string* label) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  DCHECK(type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE ||
-         type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE);
 
   // Create a new request.
   StreamOptions options;
-  EnumerationCache* cache = NULL;
-  if (type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE) {
+  if (type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE)
     options.audio = true;
-    cache = &audio_enumeration_cache_;
-  } else {
+  else
     options.video = true;
-    cache = &video_enumeration_cache_;
-  }
 
   DeviceRequest new_request(requester, options,
                             render_process_id,
                             render_view_id,
                             security_origin);
-  new_request.type = DeviceRequest::ENUMERATE_DEVICES;
-
-  if (cache->valid) {
-    // Cached device list of this type exists. Just send it out.
-    new_request.state[type] = DeviceRequest::STATE_REQUESTED;
-    AddRequest(&new_request, label);
-    // Need to post a task since the requester won't have label till
-    // this function returns.
-    BrowserThread::PostTask(BrowserThread::IO,
-        FROM_HERE,
-        base::Bind(&MediaStreamManager::SendCachedDeviceList,
-                   base::Unretained(this), cache, *label));
-  } else {
-    StartEnumeration(&new_request, label);
-    StartMonitoring();
-  }
-}
-
-void MediaStreamManager::StopEnumerateDevices(const std::string& label) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
+  new_request.type = DeviceRequest::kEnumerateDevices;
 
-  DeviceRequests::iterator it = requests_.find(label);
-  if (it != requests_.end()) {
-    DCHECK_EQ(it->second.type, DeviceRequest::ENUMERATE_DEVICES);
-    requests_.erase(it);
-    if (!HasEnumerationRequest()) {
-      StopMonitoring();
-    }
-  }
+  StartEnumeration(&new_request, label);
 }
 
 void MediaStreamManager::OpenDevice(
@@ -361,47 +310,12 @@ void MediaStreamManager::OpenDevice(
                             render_process_id,
                             render_view_id,
                             security_origin);
-  new_request.type = DeviceRequest::OPEN_DEVICE;
+  new_request.type = DeviceRequest::kOpenDevice;
   new_request.requested_device_id = device_id;
 
   StartEnumeration(&new_request, label);
 }
 
-void MediaStreamManager::SendCachedDeviceList(
-    EnumerationCache* cache,
-    const std::string& label) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  if (cache->valid) {
-    DeviceRequests::iterator it = requests_.find(label);
-    if (it != requests_.end()) {
-      it->second.requester->DevicesEnumerated(label, cache->devices);
-    }
-  }
-}
-
-void MediaStreamManager::StartMonitoring() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  if (!monitoring_started_) {
-    monitoring_started_ = true;
-    base::SystemMonitor::Get()->AddDevicesChangedObserver(this);
-  }
-}
-
-void MediaStreamManager::StopMonitoring() {
-  DCHECK_EQ(MessageLoop::current(), io_loop_);
-  if (monitoring_started_ && !HasEnumerationRequest()) {
-    base::SystemMonitor::Get()->RemoveDevicesChangedObserver(this);
-    monitoring_started_ = false;
-    ClearEnumerationCache(&audio_enumeration_cache_);
-    ClearEnumerationCache(&video_enumeration_cache_);
-  }
-}
-
-void MediaStreamManager::ClearEnumerationCache(EnumerationCache* cache) {
-  DCHECK_EQ(MessageLoop::current(), io_loop_);
-  cache->valid = false;
-}
-
 void MediaStreamManager::StartEnumeration(
     DeviceRequest* new_request,
     std::string* label) {
@@ -409,31 +323,21 @@ void MediaStreamManager::StartEnumeration(
 
   MediaStreamType stream_type = content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE;
   if (Requested(new_request->options, stream_type)) {
-    new_request->state[stream_type] = DeviceRequest::STATE_REQUESTED;
-    DCHECK_GE(active_enumeration_ref_count_[stream_type], 0);
-    if (!active_enumeration_ref_count_[stream_type]) {
-      ++active_enumeration_ref_count_[stream_type];
+    new_request->state[stream_type] = DeviceRequest::kRequested;
+    if (!enumeration_in_progress_[stream_type]) {
+      enumeration_in_progress_[stream_type] = true;
       GetDeviceManager(stream_type)->EnumerateDevices();
     }
   }
   stream_type = content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE;
   if (Requested(new_request->options, stream_type)) {
-    new_request->state[stream_type] = DeviceRequest::STATE_REQUESTED;
-    DCHECK_GE(active_enumeration_ref_count_[stream_type], 0);
-    if (!active_enumeration_ref_count_[stream_type]) {
-      ++active_enumeration_ref_count_[stream_type];
+    new_request->state[stream_type] = DeviceRequest::kRequested;
+    if (!enumeration_in_progress_[stream_type]) {
+      enumeration_in_progress_[stream_type] = true;
       GetDeviceManager(stream_type)->EnumerateDevices();
     }
   }
 
-  AddRequest(new_request, label);
-}
-
-void MediaStreamManager::AddRequest(
-    DeviceRequest* new_request,
-    std::string* label) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-
   // Create a label for this request and verify it is unique.
   std::string request_label;
   do {
@@ -442,6 +346,19 @@ void MediaStreamManager::AddRequest(
 
   requests_.insert(std::make_pair(request_label, *new_request));
 
+  // Get user confirmation to use capture devices.
+  // Need to make an asynchronous call to make sure the |requester| gets the
+  // |label| before it would receive any event.
+  if (new_request->type == DeviceRequest::kGenerateStream) {
+    BrowserThread::PostTask(BrowserThread::IO,
+        FROM_HERE,
+        base::Bind(&MediaStreamDeviceSettings::RequestCaptureDeviceUsage,
+                   base::Unretained(device_settings_.get()),
+                   request_label, new_request->render_process_id,
+                   new_request->render_view_id, new_request->options,
+                   new_request->security_origin));
+  }
+
   (*label) = request_label;
 }
 
@@ -497,7 +414,7 @@ void MediaStreamManager::Opened(MediaStreamType stream_type,
     return;
   }
 
-  DCHECK_NE(request->state[stream_type], DeviceRequest::STATE_REQUESTED);
+  DCHECK_NE(request->state[stream_type], DeviceRequest::kRequested);
 
   // Check if all devices for this stream type are opened. Update the state if
   // they are.
@@ -508,7 +425,7 @@ void MediaStreamManager::Opened(MediaStreamType stream_type,
       return;
     }
   }
-  request->state[stream_type] = DeviceRequest::STATE_DONE;
+  request->state[stream_type] = DeviceRequest::kDone;
 
   if (!RequestDone(*request)) {
     // This stream_type is done, but not the other type.
@@ -516,10 +433,10 @@ void MediaStreamManager::Opened(MediaStreamType stream_type,
   }
 
   switch (request->type) {
-    case DeviceRequest::OPEN_DEVICE:
+    case DeviceRequest::kOpenDevice:
       request->requester->DeviceOpened(label, (*devices)[0]);
       break;
-    case DeviceRequest::GENERATE_STREAM:
+    case DeviceRequest::kGenerateStream:
       request->requester->StreamGenerated(label, request->audio_devices,
                                           request->video_devices);
       NotifyObserverDevicesOpened(request);
@@ -538,21 +455,6 @@ void MediaStreamManager::DevicesEnumerated(
     MediaStreamType stream_type, const StreamDeviceInfoArray& devices) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
-  // Only cache device list when there is EnumerateDevices request, since
-  // other requests don't turn on device monitoring.
-  bool need_update_clients = false;
-  EnumerationCache* cache =
-      (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE ?
-       &audio_enumeration_cache_ : &video_enumeration_cache_);
-  if (HasEnumerationRequest(stream_type) &&
-      (!cache->valid ||
-       !std::equal(devices.begin(), devices.end(), cache->devices.begin(),
-                   media_stream::StreamDeviceInfo::IsEqual))) {
-    cache->valid = true;
-    cache->devices = devices;
-    need_update_clients = true;
-  }
-
   // Publish the result for all requests waiting for device list(s).
   // Find the requests waiting for this device list, store their labels and
   // release the iterator before calling device settings. We might get a call
@@ -560,10 +462,9 @@ void MediaStreamManager::DevicesEnumerated(
   std::list<std::string> label_list;
   for (DeviceRequests::iterator it = requests_.begin(); it != requests_.end();
        ++it) {
-    if (it->second.state[stream_type] == DeviceRequest::STATE_REQUESTED &&
+    if (it->second.state[stream_type] == DeviceRequest::kRequested &&
         Requested(it->second.options, stream_type)) {
-      if (it->second.type != DeviceRequest::ENUMERATE_DEVICES)
-        it->second.state[stream_type] = DeviceRequest::STATE_PENDING_APPROVAL;
+      it->second.state[stream_type] = DeviceRequest::kPendingApproval;
       label_list.push_back(it->first);
     }
   }
@@ -571,11 +472,11 @@ void MediaStreamManager::DevicesEnumerated(
        it != label_list.end(); ++it) {
     DeviceRequest& request = requests_[*it];
     switch (request.type) {
-      case DeviceRequest::ENUMERATE_DEVICES:
-        if (need_update_clients)
-          request.requester->DevicesEnumerated(*it, devices);
+      case DeviceRequest::kEnumerateDevices:
+        request.requester->DevicesEnumerated(*it, devices);
+        requests_.erase(*it);
         break;
-      case DeviceRequest::OPEN_DEVICE:
+      case DeviceRequest::kOpenDevice:
         for (StreamDeviceInfoArray::const_iterator device_it = devices.begin();
              device_it != devices.end(); device_it++) {
           if (request.requested_device_id == device_it->device_id) {
@@ -583,8 +484,7 @@ void MediaStreamManager::DevicesEnumerated(
             device.in_use = false;
             device.session_id =
                 GetDeviceManager(device_it->stream_type)->Open(device);
-            request.state[device_it->stream_type] =
-                DeviceRequest::STATE_OPENING;
+            request.state[device_it->stream_type] = DeviceRequest::kOpening;
             if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE)
               request.audio_devices.push_back(device);
             else
@@ -602,8 +502,7 @@ void MediaStreamManager::DevicesEnumerated(
     }
   }
   label_list.clear();
-  --active_enumeration_ref_count_[stream_type];
-  DCHECK_GE(active_enumeration_ref_count_[stream_type], 0);
+  enumeration_in_progress_[stream_type] = false;
 }
 
 void MediaStreamManager::Error(MediaStreamType stream_type,
@@ -627,7 +526,7 @@ void MediaStreamManager::Error(MediaStreamType stream_type,
          device_it != devices->end(); ++device_it, ++device_idx) {
       if (device_it->session_id == capture_session_id) {
         // We've found the failing device. Find the error case:
-        if (it->second.state[stream_type] == DeviceRequest::STATE_DONE) {
+        if (it->second.state[stream_type] == DeviceRequest::kDone) {
           // 1. Already opened -> signal device failure and close device.
           //    Use device_idx to signal which of the devices encountered an
           //    error.
@@ -677,12 +576,12 @@ void MediaStreamManager::DevicesAccepted(const std::string& label,
       // opened. in_use might be true if the device type can be used in more
       // than one session.
       DCHECK_EQ(request_it->second.state[device_it->stream_type],
-                DeviceRequest::STATE_PENDING_APPROVAL);
+                DeviceRequest::kPendingApproval);
       device_info.in_use = false;
       device_info.session_id =
           GetDeviceManager(device_info.stream_type)->Open(device_info);
       request_it->second.state[device_it->stream_type] =
-          DeviceRequest::STATE_OPENING;
+          DeviceRequest::kOpening;
       if (device_info.stream_type ==
           content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE) {
         request_it->second.audio_devices.push_back(device_info);
@@ -698,12 +597,12 @@ void MediaStreamManager::DevicesAccepted(const std::string& label,
         content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE;
     if (Requested(request_it->second.options, stream_type) &&
         request_it->second.audio_devices.size() == 0) {
-      request_it->second.state[stream_type] = DeviceRequest::STATE_ERROR;
+      request_it->second.state[stream_type] = DeviceRequest::kError;
     }
     stream_type = content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE;
     if (Requested(request_it->second.options, stream_type) &&
         request_it->second.video_devices.size() == 0) {
-      request_it->second.state[stream_type] = DeviceRequest::STATE_ERROR;
+      request_it->second.state[stream_type] = DeviceRequest::kError;
     }
     return;
   }
@@ -714,7 +613,7 @@ void MediaStreamManager::SettingsError(const std::string& label) {
   // Erase this request and report an error.
   DeviceRequests::iterator it = requests_.find(label);
   if (it != requests_.end()) {
-    DCHECK_EQ(it->second.type, DeviceRequest::GENERATE_STREAM);
+    DCHECK_EQ(it->second.type, DeviceRequest::kGenerateStream);
     it->second.requester->StreamGenerationFailed(label);
     requests_.erase(it);
     return;
@@ -729,10 +628,7 @@ void MediaStreamManager::UseFakeDevice() {
 
 void MediaStreamManager::WillDestroyCurrentMessageLoop() {
   DCHECK_EQ(MessageLoop::current(), io_loop_);
-  DCHECK(requests_.empty());
   if (device_thread_.get()) {
-    StopMonitoring();
-
     video_capture_manager_->Unregister();
     audio_input_device_manager_->Unregister();
     device_thread_.reset();
@@ -825,57 +721,4 @@ MediaStreamProvider* MediaStreamManager::GetDeviceManager(
   return NULL;
 }
 
-void MediaStreamManager::OnDevicesChanged(
-    base::SystemMonitor::DeviceType device_type) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  MediaStreamType stream_type;
-  EnumerationCache* cache;
-  if (device_type == base::SystemMonitor::DEVTYPE_AUDIO_CAPTURE) {
-    stream_type = content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE;
-    cache = &audio_enumeration_cache_;
-  } else if (device_type == base::SystemMonitor::DEVTYPE_VIDEO_CAPTURE) {
-    stream_type = content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE;
-    cache = &video_enumeration_cache_;
-  } else {
-    return;  // Uninteresting device change.
-  }
-
-  if (!HasEnumerationRequest(stream_type)) {
-    // There is no request for that type, No need to enumerate devices.
-    // Therefore, invalidate the cache of that type.
-    ClearEnumerationCache(cache);
-    return;
-  }
-
-  // Always do enumeration even though some enumeration is in progress,
-  // because those enumeration commands could be sent before these devices
-  // change.
-  ++active_enumeration_ref_count_[stream_type];
-  GetDeviceManager(stream_type)->EnumerateDevices();
-}
-
-bool MediaStreamManager::HasEnumerationRequest() {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  for (DeviceRequests::iterator it = requests_.begin();
-       it != requests_.end(); ++it) {
-    if (it->second.type == DeviceRequest::ENUMERATE_DEVICES) {
-      return true;
-    }
-  }
-  return false;
-}
-
-bool MediaStreamManager::HasEnumerationRequest(
-    MediaStreamType stream_type) {
-  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
-  for (DeviceRequests::iterator it = requests_.begin();
-       it != requests_.end(); ++it) {
-    if (it->second.type == DeviceRequest::ENUMERATE_DEVICES &&
-        Requested(it->second.options, stream_type)) {
-      return true;
-    }
-  }
-  return false;
-}
-
 }  // namespace media_stream
diff --git a/content/browser/renderer_host/media/media_stream_manager.h b/content/browser/renderer_host/media/media_stream_manager.h
index 6fb5269..648f21c 100644
--- a/content/browser/renderer_host/media/media_stream_manager.h
+++ b/content/browser/renderer_host/media/media_stream_manager.h
@@ -30,7 +30,6 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop.h"
-#include "base/system_monitor/system_monitor.h"
 #include "base/threading/thread.h"
 #include "content/browser/renderer_host/media/media_stream_provider.h"
 #include "content/browser/renderer_host/media/media_stream_settings_requester.h"
@@ -73,8 +72,7 @@ class DeviceThread : public base::Thread {
 class CONTENT_EXPORT MediaStreamManager
     : public MediaStreamProviderListener,
       public MessageLoop::DestructionObserver,
-      public SettingsRequester,
-      public base::SystemMonitor::DevicesChangedObserver {
+      public SettingsRequester {
  public:
   // This class takes the ownerships of the |audio_input_device_manager|
   // and |video_capture_manager|.
@@ -109,9 +107,6 @@ class CONTENT_EXPORT MediaStreamManager
   // Gets a list of devices of |type|.
   // The request is identified using |label|, which is pointing to a
   // std::string.
-  // The request is persistent, which means the client keeps listening to
-  // device changes, such as plug/unplug, and expects new device list for
-  // such a change, till the client stops the request.
   void EnumerateDevices(MediaStreamRequester* requester,
                         int render_process_id,
                         int render_view_id,
@@ -146,10 +141,6 @@ class CONTENT_EXPORT MediaStreamManager
                                const StreamDeviceInfoArray& devices) OVERRIDE;
   virtual void SettingsError(const std::string& label) OVERRIDE;
 
-  // Implements base::SystemMonitor::DevicesChangedObserver.
-  virtual void OnDevicesChanged(
-      base::SystemMonitor::DeviceType device_type) OVERRIDE;
-
   // Used by unit test to make sure fake devices are used instead of a real
   // devices, which is needed for server based testing.
   // TODO(xians): Remove this hack since we can create our own
@@ -165,15 +156,6 @@ class CONTENT_EXPORT MediaStreamManager
   // Contains all data needed to keep track of requests.
   struct DeviceRequest;
 
-  // Cache enumerated device list.
-  struct EnumerationCache {
-    EnumerationCache();
-    ~EnumerationCache();
-
-    bool valid;
-    StreamDeviceInfoArray devices;
-  };
-
   // Helpers for signaling the media observer that new capture devices are
   // opened/closed.
   void NotifyObserverDevicesOpened(DeviceRequest* request);
@@ -186,26 +168,11 @@ class CONTENT_EXPORT MediaStreamManager
   MediaStreamProvider* GetDeviceManager(MediaStreamType stream_type);
   void StartEnumeration(DeviceRequest* new_request,
                         std::string* label);
-  void AddRequest(DeviceRequest* new_request, std::string* label);
-  bool HasEnumerationRequest(MediaStreamType type);
-  bool HasEnumerationRequest();
-  void ClearEnumerationCache(EnumerationCache* cache);
 
   // Helper to ensure the device thread and pass the message loop to device
   // managers, it also register itself as the listener to the device managers.
   void EnsureDeviceThreadAndListener();
 
-  // Sends cached device list to a client corresponding to the request
-  // identified by |label|.
-  void SendCachedDeviceList(EnumerationCache* cache, const std::string& label);
-
-  // Stop the request of enumerating devices indentified by |label|.
-  void StopEnumerateDevices(const std::string& label);
-
-  // Helpers to start and stop monitoring devices.
-  void StartMonitoring();
-  void StopMonitoring();
-
   // Device thread shared by VideoCaptureManager and AudioInputDeviceManager.
   scoped_ptr<base::Thread> device_thread_;
 
@@ -213,17 +180,9 @@ class CONTENT_EXPORT MediaStreamManager
   scoped_refptr<AudioInputDeviceManager> audio_input_device_manager_;
   scoped_refptr<VideoCaptureManager> video_capture_manager_;
 
-  // Indicator of device monitoring state.
-  bool monitoring_started_;
-
-  // Stores most recently enumerated device lists. The cache is cleared when
-  // monitoring is stopped or there is no request for that type of device.
-  EnumerationCache audio_enumeration_cache_;
-  EnumerationCache video_enumeration_cache_;
-
-  // Keeps track of live enumeration commands sent to VideoCaptureManager or
-  // AudioInputDeviceManager, in order to only enumerate when necessary.
-  int active_enumeration_ref_count_[content::NUM_MEDIA_STREAM_DEVICE_TYPES];
+  // Keeps track of device types currently being enumerated to not enumerate
+  // when not necessary.
+  std::vector<bool> enumeration_in_progress_;
 
   // All non-closed request.
   typedef std::map<std::string, DeviceRequest> DeviceRequests;
diff --git a/content/common/media/media_stream_messages.h b/content/common/media/media_stream_messages.h
index 5c89f8d..1f87b10 100644
--- a/content/common/media/media_stream_messages.h
+++ b/content/common/media/media_stream_messages.h
@@ -55,9 +55,8 @@ IPC_MESSAGE_ROUTED2(MediaStreamHostMsg_AudioDeviceFailed,
                     int /* index */)
 
 // The browser has enumerated devices successfully.
-IPC_MESSAGE_ROUTED3(MediaStreamMsg_DevicesEnumerated,
+IPC_MESSAGE_ROUTED2(MediaStreamMsg_DevicesEnumerated,
                     int /* request id */,
-                    std::string /* label */,
                     media_stream::StreamDeviceInfoArray /* device_list */)
 
 // The browser has failed to enumerate devices.
diff --git a/content/common/media/media_stream_options.cc b/content/common/media/media_stream_options.cc
index 9daa96a..28ee038 100644
--- a/content/common/media/media_stream_options.cc
+++ b/content/common/media/media_stream_options.cc
@@ -24,14 +24,4 @@ StreamDeviceInfo::StreamDeviceInfo(MediaStreamType service_param,
       in_use(opened),
       session_id(kNoId) {}
 
-// static
-bool StreamDeviceInfo::IsEqual(const StreamDeviceInfo& first,
-                               const StreamDeviceInfo& second) {
-  return first.stream_type == second.stream_type &&
-      first.name == second.name &&
-      first.device_id == second.device_id &&
-      first.in_use == second.in_use &&
-      first.session_id == second.session_id;
-}
-
 }  // namespace media_stream
diff --git a/content/common/media/media_stream_options.h b/content/common/media/media_stream_options.h
index c51d700..e5127ed 100644
--- a/content/common/media/media_stream_options.h
+++ b/content/common/media/media_stream_options.h
@@ -39,8 +39,6 @@ struct CONTENT_EXPORT StreamDeviceInfo {
                    const std::string& name_param,
                    const std::string& device_param,
                    bool opened);
-  static bool IsEqual(const StreamDeviceInfo& first,
-                      const StreamDeviceInfo& second);
 
   // Describes the capture type.
   MediaStreamType stream_type;
diff --git a/content/renderer/media/media_stream_dispatcher.cc b/content/renderer/media/media_stream_dispatcher.cc
index 5d97ca0..ed55342 100644
--- a/content/renderer/media/media_stream_dispatcher.cc
+++ b/content/renderer/media/media_stream_dispatcher.cc
@@ -31,36 +31,8 @@ struct MediaStreamDispatcher::Stream {
   media_stream::StreamDeviceInfoArray video_array;
 };
 
-MediaStreamDispatcher::EnumerationRequest::EnumerationRequest(
-    const base::WeakPtr<MediaStreamDispatcherEventHandler>& handler,
-    int request_id)
-    : handler(handler),
-      request_id(request_id) {
-}
-
-MediaStreamDispatcher::EnumerationRequest::~EnumerationRequest() {}
-
-MediaStreamDispatcher::EnumerationState::EnumerationState()
-    : ipc_id(-1) {
-}
-
-MediaStreamDispatcher::EnumerationState::~EnumerationState() {}
-
-struct MediaStreamDispatcher::EnumerationState::CachedDevices {
-  CachedDevices(const std::string& label,
-                const media_stream::StreamDeviceInfoArray& device_array)
-      : label(label),
-        devices(device_array) {
-  }
-  ~CachedDevices() {}
-
-  std::string label;
-  media_stream::StreamDeviceInfoArray devices;
-};
-
 MediaStreamDispatcher::MediaStreamDispatcher(RenderViewImpl* render_view)
     : content::RenderViewObserver(render_view),
-      main_loop_(base::MessageLoopProxy::current()),
       next_ipc_id_(0) {
 }
 
@@ -71,7 +43,6 @@ void MediaStreamDispatcher::GenerateStream(
     const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler,
     media_stream::StreamOptions components,
     const GURL& security_origin) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::GenerateStream(" << request_id << ")";
 
   requests_.push_back(Request(event_handler, request_id, next_ipc_id_));
@@ -82,7 +53,6 @@ void MediaStreamDispatcher::GenerateStream(
 }
 
 void MediaStreamDispatcher::CancelGenerateStream(int request_id) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::CancelGenerateStream"
            << ", {request_id = " << request_id << "}";
 
@@ -99,7 +69,6 @@ void MediaStreamDispatcher::CancelGenerateStream(int request_id) {
 }
 
 void MediaStreamDispatcher::StopStream(const std::string& label) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::StopStream"
            << ", {label = " << label << "}";
 
@@ -116,64 +85,14 @@ void MediaStreamDispatcher::EnumerateDevices(
     const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler,
     media_stream::MediaStreamType type,
     const GURL& security_origin) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
-  DCHECK(type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE ||
-         type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE);
   DVLOG(1) << "MediaStreamDispatcher::EnumerateDevices("
            << request_id << ")";
 
-  EnumerationState* state =
-      (type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE ?
-       &audio_enumeration_state_ : &video_enumeration_state_);
-  state->requests.push_back(
-      EnumerationRequest(event_handler, request_id));
-
-  if (state->cached_devices.get()) {
-    event_handler->OnDevicesEnumerated(
-        request_id, state->cached_devices->devices);
-  } else if (state->ipc_id < 0) {
-    Send(new MediaStreamHostMsg_EnumerateDevices(routing_id(),
-                                                 next_ipc_id_,
-                                                 type,
-                                                 security_origin));
-    state->ipc_id = next_ipc_id_++;
-  }
-}
-
-void MediaStreamDispatcher::StopEnumerateDevices(
-    int request_id,
-    const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
-  DVLOG(1) << "MediaStreamDispatcher::StopEnumerateDevices("
-           << request_id << ")";
-
-  // Remove the request.
-  RemoveEnumerationRequest(
-      request_id, event_handler, &audio_enumeration_state_);
-  RemoveEnumerationRequest(
-      request_id, event_handler, &video_enumeration_state_);
-}
-
-void MediaStreamDispatcher::RemoveEnumerationRequest(
-    int request_id,
-    const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler,
-    EnumerationState* state) {
-  EnumerationRequestList* requests = &state->requests;
-  for (EnumerationRequestList::iterator it = requests->begin();
-       it != requests->end(); ++it) {
-    if (it->request_id == request_id && it->handler == event_handler) {
-      requests->erase(it);
-      if (requests->empty() && !state->cached_devices.get()) {
-        // No more request and has a label, try to stop the label
-        // and invalidate the state.
-        Send(new MediaStreamHostMsg_StopGeneratedStream(
-            routing_id(), state->cached_devices->label));
-        state->ipc_id = -1;
-        state->cached_devices.reset();
-      }
-      return;
-    }
-  }
+  requests_.push_back(Request(event_handler, request_id, next_ipc_id_));
+  Send(new MediaStreamHostMsg_EnumerateDevices(routing_id(),
+                                               next_ipc_id_++,
+                                               type,
+                                               security_origin));
 }
 
 void MediaStreamDispatcher::OpenDevice(
@@ -182,7 +101,6 @@ void MediaStreamDispatcher::OpenDevice(
     const std::string& device_id,
     media_stream::MediaStreamType type,
     const GURL& security_origin) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::OpenDevice(" << request_id << ")";
 
   requests_.push_back(Request(event_handler, request_id, next_ipc_id_));
@@ -194,7 +112,6 @@ void MediaStreamDispatcher::OpenDevice(
 }
 
 void MediaStreamDispatcher::CloseDevice(const std::string& label) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::CloseDevice"
            << ", {label = " << label << "}";
 
@@ -230,7 +147,6 @@ void MediaStreamDispatcher::OnStreamGenerated(
     const std::string& label,
     const media_stream::StreamDeviceInfoArray& audio_array,
     const media_stream::StreamDeviceInfoArray& video_array) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
 
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
@@ -254,7 +170,6 @@ void MediaStreamDispatcher::OnStreamGenerated(
 }
 
 void MediaStreamDispatcher::OnStreamGenerationFailed(int request_id) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
     Request& request = *it;
@@ -272,7 +187,6 @@ void MediaStreamDispatcher::OnStreamGenerationFailed(int request_id) {
 
 void MediaStreamDispatcher::OnVideoDeviceFailed(const std::string& label,
                                                 int index) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   LabelStreamMap::iterator it = label_stream_map_.find(label);
   if (it == label_stream_map_.end())
     return;
@@ -288,7 +202,6 @@ void MediaStreamDispatcher::OnVideoDeviceFailed(const std::string& label,
 
 void MediaStreamDispatcher::OnAudioDeviceFailed(const std::string& label,
                                                 int index) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   LabelStreamMap::iterator it = label_stream_map_.find(label);
   if (it == label_stream_map_.end())
     return;
@@ -304,41 +217,24 @@ void MediaStreamDispatcher::OnAudioDeviceFailed(const std::string& label,
 
 void MediaStreamDispatcher::OnDevicesEnumerated(
     int request_id,
-    const std::string& label,
     const media_stream::StreamDeviceInfoArray& device_array) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
-  DCHECK_GE(request_id, 0);
-
-  EnumerationState* state;
-  if (request_id == audio_enumeration_state_.ipc_id) {
-    state = &audio_enumeration_state_;
-  } else if (request_id == video_enumeration_state_.ipc_id) {
-    state = &video_enumeration_state_;
-  } else {
-    // This could happen when requester has stopped enumeration while some
-    // enumerated response is on the way. Have to stop the |label| because
-    // this might be the first enumerated device list is received. This also
-    // lead to same label being stopped multiple times.
-    Send(new MediaStreamHostMsg_StopGeneratedStream(routing_id(), label));
-    return;
-  }
 
-  DCHECK(!label.empty());
-  state->cached_devices.reset(new EnumerationState::CachedDevices(
-      label, device_array));
-
-  for (EnumerationRequestList::iterator it = state->requests.begin();
-       it != state->requests.end(); ++it) {
-    if (it->handler) {
-      it->handler->OnDevicesEnumerated(it->request_id, device_array);
-      DVLOG(1) << "MediaStreamDispatcher::OnDevicesEnumerated("
-               << it->request_id << ")";
+  for (RequestList::iterator it = requests_.begin();
+       it != requests_.end(); ++it) {
+    Request& request = *it;
+    if (request.ipc_request == request_id) {
+      if (request.handler) {
+        request.handler->OnDevicesEnumerated(request.request_id, device_array);
+        DVLOG(1) << "MediaStreamDispatcher::OnDevicesEnumerated("
+                 << request.request_id << ")";
+      }
+      requests_.erase(it);
+      break;
     }
   }
 }
 
 void MediaStreamDispatcher::OnDevicesEnumerationFailed(int request_id) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
     Request& request = *it;
@@ -358,7 +254,6 @@ void MediaStreamDispatcher::OnDeviceOpened(
     int request_id,
     const std::string& label,
     const media_stream::StreamDeviceInfo& device_info) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
     Request& request = *it;
@@ -385,7 +280,6 @@ void MediaStreamDispatcher::OnDeviceOpened(
 }
 
 void MediaStreamDispatcher::OnDeviceOpenFailed(int request_id) {
-  DCHECK(main_loop_->BelongsToCurrentThread());
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
     Request& request = *it;
diff --git a/content/renderer/media/media_stream_dispatcher.h b/content/renderer/media/media_stream_dispatcher.h
index fc1145b..a000c52 100644
--- a/content/renderer/media/media_stream_dispatcher.h
+++ b/content/renderer/media/media_stream_dispatcher.h
@@ -11,17 +11,12 @@
 
 #include "base/basictypes.h"
 #include "base/gtest_prod_util.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/memory/weak_ptr.h"
+#include "base/message_loop.h"
 #include "content/common/content_export.h"
 #include "content/common/media/media_stream_options.h"
 #include "content/public/renderer/render_view_observer.h"
 #include "content/renderer/media/media_stream_dispatcher_eventhandler.h"
 
-namespace base {
-class MessageLoopProxy;
-}
-
 class RenderViewImpl;
 
 // MediaStreamDispatcher is a delegate for the Media Stream API messages.
@@ -57,11 +52,6 @@ class CONTENT_EXPORT MediaStreamDispatcher
       media_stream::MediaStreamType type,
       const GURL& security_origin);
 
-  // Request to stop enumerating devices.
-  void StopEnumerateDevices(
-      int request_id,
-      const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler);
-
   // Request to open a device.
   void OpenDevice(
       int request_id,
@@ -93,31 +83,6 @@ class CONTENT_EXPORT MediaStreamDispatcher
   // opened it.
   struct Stream;
 
-  struct EnumerationRequest {
-    EnumerationRequest(
-        const base::WeakPtr<MediaStreamDispatcherEventHandler>& handler,
-        int request_id);
-    ~EnumerationRequest();
-
-    base::WeakPtr<MediaStreamDispatcherEventHandler> handler;
-    int request_id;
-  };
-
-  // List of requests made to EnumerateDevices.
-  typedef std::list<EnumerationRequest> EnumerationRequestList;
-
-  struct EnumerationState {
-    EnumerationState();
-    ~EnumerationState();
-
-    struct CachedDevices;
-
-    // If |ipc_id| >= 0, then we've started.
-    int ipc_id;
-    scoped_ptr<CachedDevices> cached_devices;
-    EnumerationRequestList requests;
-  };
-
   // Messages from the browser.
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
   void OnStreamGenerated(
@@ -130,7 +95,6 @@ class CONTENT_EXPORT MediaStreamDispatcher
   void OnAudioDeviceFailed(const std::string& label, int index);
   void OnDevicesEnumerated(
       int request_id,
-      const std::string& label,
       const media_stream::StreamDeviceInfoArray& device_array);
   void OnDevicesEnumerationFailed(int request_id);
   void OnDeviceOpened(
@@ -139,21 +103,10 @@ class CONTENT_EXPORT MediaStreamDispatcher
       const media_stream::StreamDeviceInfo& device_info);
   void OnDeviceOpenFailed(int request_id);
 
-  void RemoveEnumerationRequest(
-      int request_id,
-      const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler,
-      EnumerationState* state);
-
-  // Used for DCHECKs so methods calls won't execute in the wrong thread.
-  scoped_refptr<base::MessageLoopProxy> main_loop_;
-
   int next_ipc_id_;
   typedef std::map<std::string, Stream> LabelStreamMap;
   LabelStreamMap label_stream_map_;
 
-  EnumerationState audio_enumeration_state_;
-  EnumerationState video_enumeration_state_;
-
   // List of calls made to GenerateStream that has not yet completed.
   typedef std::list<Request> RequestList;
   RequestList requests_;
diff --git a/content/renderer/media/media_stream_dispatcher_unittest.cc b/content/renderer/media/media_stream_dispatcher_unittest.cc
index 458d61b..c83c8b3 100644
--- a/content/renderer/media/media_stream_dispatcher_unittest.cc
+++ b/content/renderer/media/media_stream_dispatcher_unittest.cc
@@ -22,7 +22,6 @@ const int kRequestId1 = 10;
 const int kRequestId2 = 20;
 const int kRequestId3 = 30;
 const int kRequestId4 = 40;
-static const char kLabel[] = "test";
 
 class MockMediaStreamDispatcherEventHandler
     : public MediaStreamDispatcherEventHandler,
@@ -89,7 +88,6 @@ class MockMediaStreamDispatcherEventHandler
 }  // namespace
 
 TEST(MediaStreamDispatcherTest, BasicStream) {
-  scoped_ptr<MessageLoop> message_loop(new MessageLoop());
   scoped_ptr<MediaStreamDispatcher> dispatcher(new MediaStreamDispatcher(NULL));
   scoped_ptr<MockMediaStreamDispatcherEventHandler>
       handler(new MockMediaStreamDispatcherEventHandler);
@@ -165,24 +163,21 @@ TEST(MediaStreamDispatcherTest, BasicStream) {
 }
 
 TEST(MediaStreamDispatcherTest, BasicVideoDevice) {
-  scoped_ptr<MessageLoop> message_loop(new MessageLoop());
   scoped_ptr<MediaStreamDispatcher> dispatcher(new MediaStreamDispatcher(NULL));
   scoped_ptr<MockMediaStreamDispatcherEventHandler>
-      handler1(new MockMediaStreamDispatcherEventHandler);
-  scoped_ptr<MockMediaStreamDispatcherEventHandler>
-      handler2(new MockMediaStreamDispatcherEventHandler);
+      handler(new MockMediaStreamDispatcherEventHandler);
   GURL security_origin;
 
   int ipc_request_id1 = dispatcher->next_ipc_id_;
-  dispatcher->EnumerateDevices(kRequestId1, handler1.get()->AsWeakPtr(),
+  dispatcher->EnumerateDevices(kRequestId1, handler.get()->AsWeakPtr(),
                                content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE,
                                security_origin);
   int ipc_request_id2 = dispatcher->next_ipc_id_;
   EXPECT_NE(ipc_request_id1, ipc_request_id2);
-  dispatcher->EnumerateDevices(kRequestId2, handler2.get()->AsWeakPtr(),
+  dispatcher->EnumerateDevices(kRequestId2, handler.get()->AsWeakPtr(),
                                content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE,
                                security_origin);
-  EXPECT_EQ(dispatcher->video_enumeration_state_.requests.size(), size_t(2));
+  EXPECT_EQ(dispatcher->requests_.size(), size_t(2));
 
   media_stream::StreamDeviceInfoArray video_device_array(1);
   media_stream::StreamDeviceInfo video_device_info;
@@ -193,23 +188,27 @@ TEST(MediaStreamDispatcherTest, BasicVideoDevice) {
   video_device_info.session_id = kVideoSessionId;
   video_device_array[0] = video_device_info;
 
-  // Complete the enumeration request and all requesters should receive reply.
+  // Complete the enumeration of request 1.
+  dispatcher->OnMessageReceived(MediaStreamMsg_DevicesEnumerated(
+      kRouteId, ipc_request_id1, video_device_array));
+  EXPECT_EQ(handler->request_id_, kRequestId1);
+
+  // Complete the enumeration of request 2.
   dispatcher->OnMessageReceived(MediaStreamMsg_DevicesEnumerated(
-      kRouteId, ipc_request_id1, kLabel, video_device_array));
-  EXPECT_EQ(handler1->request_id_, kRequestId1);
-  EXPECT_EQ(handler2->request_id_, kRequestId2);
+      kRouteId, ipc_request_id2, video_device_array));
+  EXPECT_EQ(handler->request_id_, kRequestId2);
 
-  EXPECT_EQ(dispatcher->video_enumeration_state_.requests.size(), size_t(2));
+  EXPECT_EQ(dispatcher->requests_.size(), size_t(0));
   EXPECT_EQ(dispatcher->label_stream_map_.size(), size_t(0));
 
   int ipc_request_id3 = dispatcher->next_ipc_id_;
-  dispatcher->OpenDevice(kRequestId3, handler1.get()->AsWeakPtr(),
+  dispatcher->OpenDevice(kRequestId3, handler.get()->AsWeakPtr(),
                          video_device_info.device_id,
                          content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE,
                          security_origin);
   int ipc_request_id4 = dispatcher->next_ipc_id_;
   EXPECT_NE(ipc_request_id3, ipc_request_id4);
-  dispatcher->OpenDevice(kRequestId4, handler1.get()->AsWeakPtr(),
+  dispatcher->OpenDevice(kRequestId4, handler.get()->AsWeakPtr(),
                          video_device_info.device_id,
                          content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE,
                          security_origin);
@@ -219,13 +218,13 @@ TEST(MediaStreamDispatcherTest, BasicVideoDevice) {
   std::string stream_label1 = std::string("stream1");
   dispatcher->OnMessageReceived(MediaStreamMsg_DeviceOpened(
       kRouteId, ipc_request_id3, stream_label1, video_device_info));
-  EXPECT_EQ(handler1->request_id_, kRequestId3);
+  EXPECT_EQ(handler->request_id_, kRequestId3);
 
   // Complete the OpenDevice of request 2.
   std::string stream_label2 = std::string("stream2");
   dispatcher->OnMessageReceived(MediaStreamMsg_DeviceOpened(
       kRouteId, ipc_request_id4, stream_label2, video_device_info));
-  EXPECT_EQ(handler1->request_id_, kRequestId4);
+  EXPECT_EQ(handler->request_id_, kRequestId4);
 
   EXPECT_EQ(dispatcher->requests_.size(), size_t(0));
   EXPECT_EQ(dispatcher->label_stream_map_.size(), size_t(2));
@@ -251,7 +250,6 @@ TEST(MediaStreamDispatcherTest, BasicVideoDevice) {
 }
 
 TEST(MediaStreamDispatcherTest, TestFailure) {
-  scoped_ptr<MessageLoop> message_loop(new MessageLoop());
   scoped_ptr<MediaStreamDispatcher> dispatcher(new MediaStreamDispatcher(NULL));
   scoped_ptr<MockMediaStreamDispatcherEventHandler>
       handler(new MockMediaStreamDispatcherEventHandler);
@@ -318,7 +316,6 @@ TEST(MediaStreamDispatcherTest, TestFailure) {
 }
 
 TEST(MediaStreamDispatcherTest, CancelGenerateStream) {
-  scoped_ptr<MessageLoop> message_loop(new MessageLoop());
   scoped_ptr<MediaStreamDispatcher> dispatcher(new MediaStreamDispatcher(NULL));
   scoped_ptr<MockMediaStreamDispatcherEventHandler>
       handler(new MockMediaStreamDispatcherEventHandler);
diff --git a/content/renderer/pepper/pepper_device_enumeration_event_handler.cc b/content/renderer/pepper/pepper_device_enumeration_event_handler.cc
index 3ea089c..d5a1d20 100644
--- a/content/renderer/pepper/pepper_device_enumeration_event_handler.cc
+++ b/content/renderer/pepper/pepper_device_enumeration_event_handler.cc
@@ -127,8 +127,7 @@ void PepperDeviceEnumerationEventHandler::NotifyDevicesEnumerated(
     const media_stream::StreamDeviceInfoArray& device_array) {
   EnumerateCallbackMap::iterator iter = enumerate_callbacks_.find(request_id);
   if (iter == enumerate_callbacks_.end()) {
-    // This might be enumerated result sent before StopEnumerateDevices is
-    // called since EnumerateDevices is persistent request.
+    NOTREACHED();
     return;
   }
 
diff --git a/content/renderer/pepper/pepper_plugin_delegate_impl.cc b/content/renderer/pepper/pepper_plugin_delegate_impl.cc
index c8fc294..351b0a0 100644
--- a/content/renderer/pepper/pepper_plugin_delegate_impl.cc
+++ b/content/renderer/pepper/pepper_plugin_delegate_impl.cc
@@ -1506,19 +1506,6 @@ int PepperPluginDelegateImpl::EnumerateDevices(
   return request_id;
 }
 
-void PepperPluginDelegateImpl::StopEnumerateDevices(int request_id) {
-#if defined(ENABLE_WEBRTC)
-  // Need to post task since this function might be called inside the callback
-  // of EnumerateDevices.
-  MessageLoop::current()->PostTask(
-      FROM_HERE,
-      base::Bind(
-          &MediaStreamDispatcher::StopEnumerateDevices,
-          base::Unretained(render_view_->media_stream_dispatcher()),
-          request_id, device_enumeration_event_handler_.get()->AsWeakPtr()));
-#endif
-}
-
 bool PepperPluginDelegateImpl::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(PepperPluginDelegateImpl, message)
diff --git a/content/renderer/pepper/pepper_plugin_delegate_impl.h b/content/renderer/pepper/pepper_plugin_delegate_impl.h
index 09e3986..83d3103 100644
--- a/content/renderer/pepper/pepper_plugin_delegate_impl.h
+++ b/content/renderer/pepper/pepper_plugin_delegate_impl.h
@@ -377,7 +377,6 @@ class PepperPluginDelegateImpl
   virtual int EnumerateDevices(
       PP_DeviceType_Dev type,
       const EnumerateDevicesCallback& callback) OVERRIDE;
-  virtual void StopEnumerateDevices(int request_id) OVERRIDE;
   virtual webkit_glue::ClipboardClient* CreateClipboardClient() const OVERRIDE;
   virtual std::string GetDeviceID() OVERRIDE;
   virtual PP_FlashLSORestrictions GetLocalDataRestrictions(
diff --git a/webkit/plugins/ppapi/mock_plugin_delegate.cc b/webkit/plugins/ppapi/mock_plugin_delegate.cc
index 782c728..298ddc9 100644
--- a/webkit/plugins/ppapi/mock_plugin_delegate.cc
+++ b/webkit/plugins/ppapi/mock_plugin_delegate.cc
@@ -451,9 +451,6 @@ int MockPluginDelegate::EnumerateDevices(
   return -1;
 }
 
-void MockPluginDelegate::StopEnumerateDevices(int request_id) {
-}
-
 webkit_glue::ClipboardClient*
 MockPluginDelegate::CreateClipboardClient() const {
   return NULL;
diff --git a/webkit/plugins/ppapi/mock_plugin_delegate.h b/webkit/plugins/ppapi/mock_plugin_delegate.h
index 038bd25..3fa4677 100644
--- a/webkit/plugins/ppapi/mock_plugin_delegate.h
+++ b/webkit/plugins/ppapi/mock_plugin_delegate.h
@@ -202,7 +202,6 @@ class MockPluginDelegate : public PluginDelegate {
   virtual bool IsPageVisible() const;
   virtual int EnumerateDevices(PP_DeviceType_Dev type,
                                const EnumerateDevicesCallback& callback);
-  virtual void StopEnumerateDevices(int request_id);
   virtual webkit_glue::ClipboardClient* CreateClipboardClient() const;
   virtual std::string GetDeviceID();
   virtual PP_FlashLSORestrictions GetLocalDataRestrictions(
diff --git a/webkit/plugins/ppapi/plugin_delegate.h b/webkit/plugins/ppapi/plugin_delegate.h
index fd8a2a5..ab237a3 100644
--- a/webkit/plugins/ppapi/plugin_delegate.h
+++ b/webkit/plugins/ppapi/plugin_delegate.h
@@ -659,9 +659,6 @@ class PluginDelegate {
   // callback will be the same as the return value.
   virtual int EnumerateDevices(PP_DeviceType_Dev type,
                                const EnumerateDevicesCallback& callback) = 0;
-  // Stop enumerating devices of the specified |request_id|. The |request_id|
-  // is the return value of EnumerateDevicesCallback.
-  virtual void StopEnumerateDevices(int request_id) = 0;
   // Create a ClipboardClient for writing to the clipboard. The caller will own
   // the pointer to this.
   virtual webkit_glue::ClipboardClient* CreateClipboardClient() const = 0;
diff --git a/webkit/plugins/ppapi/ppb_audio_input_impl.cc b/webkit/plugins/ppapi/ppb_audio_input_impl.cc
index f4f40c0..3b4d609 100644
--- a/webkit/plugins/ppapi/ppb_audio_input_impl.cc
+++ b/webkit/plugins/ppapi/ppb_audio_input_impl.cc
@@ -175,10 +175,6 @@ void PPB_AudioInput_Impl::EnumerateDevicesCallbackFunc(
   if (succeeded)
     devices_data_ = devices;
 
-  PluginDelegate* plugin_delegate = ResourceHelper::GetPluginDelegate(this);
-  if (plugin_delegate)
-    plugin_delegate->StopEnumerateDevices(request_id);
-
   OnEnumerateDevicesComplete(succeeded ? PP_OK : PP_ERROR_FAILED, devices);
 }
 
diff --git a/webkit/plugins/ppapi/ppb_video_capture_impl.cc b/webkit/plugins/ppapi/ppb_video_capture_impl.cc
index caf9027..a39f46a 100644
--- a/webkit/plugins/ppapi/ppb_video_capture_impl.cc
+++ b/webkit/plugins/ppapi/ppb_video_capture_impl.cc
@@ -312,10 +312,6 @@ void PPB_VideoCapture_Impl::EnumerateDevicesCallbackFunc(
   if (succeeded)
     devices_data_ = devices;
 
-  PluginInstance* instance = ResourceHelper::GetPluginInstance(this);
-  if (instance)
-    instance->delegate()->StopEnumerateDevices(request_id);
-
   OnEnumerateDevicesComplete(succeeded ? PP_OK : PP_ERROR_FAILED, devices);
 }