refactor EnumerateDevices to make it a persistent request.

content/browser/renderer_host/media/media_stream_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 "content/browser/renderer_host/media/media_stream_manager.h"
 
 #include <list>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 29 matching lines @@
   for (size_t i = 0; i < label.size(); ++i) {
     int random_char = base::RandGenerator(sizeof(kAlphabet) - 1);
     label[i] = kAlphabet[random_char];
   }
   return label;
 }
 
 // Helper to verify if a media stream type is part of options or not.
 static bool Requested(const StreamOptions& options,
                       MediaStreamType stream_type) {
-  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;
+  return (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE &&
+          options.video) ||
+         (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE &&
+          options.audio);
 }
 
 DeviceThread::DeviceThread(const char* name)
     : base::Thread(name) {
 }
 
 DeviceThread::~DeviceThread() {
   Stop();
 }
 
 void DeviceThread::Init() {
   using base::win::ScopedCOMInitializer;
   // Enter the multi-threaded apartment.
   com_initializer_.reset(new ScopedCOMInitializer(ScopedCOMInitializer::kMTA));
 }
 
 void DeviceThread::CleanUp() {
   com_initializer_.reset();
 }
 
 // TODO(xians): Merge DeviceRequest with MediaStreamRequest.
 struct MediaStreamManager::DeviceRequest {
   enum RequestState {
-    kNotRequested = 0,
-    kRequested,
-    kPendingApproval,
-    kOpening,
-    kDone,
-    kError
+    STATE_NOT_REQUESTED = 0,
+    STATE_REQUESTED,
+    STATE_PENDING_APPROVAL,
+    STATE_OPENING,
+    STATE_DONE,
+    STATE_ERROR
   };
 
   enum RequestType {
-    kGenerateStream = 0,
-    kEnumerateDevices,
-    kOpenDevice
+    GENERATE_STREAM = 0,
+    ENUMERATE_DEVICES,
+    OPEN_DEVICE
   };
 
   DeviceRequest()
       : requester(NULL),
-        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, kNotRequested),
-        type(kGenerateStream),
+        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, STATE_NOT_REQUESTED),
+        type(GENERATE_STREAM),
         render_process_id(-1),
         render_view_id(-1) {
     options.audio = false;
     options.video = false;
   }
 
   DeviceRequest(MediaStreamRequester* requester,
                 const StreamOptions& request_options,
                 int render_process_id,
                 int render_view_id,
                 const GURL& request_security_origin)
       : requester(requester),
         options(request_options),
-        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, kNotRequested),
-        type(kGenerateStream),
+        state(content::NUM_MEDIA_STREAM_DEVICE_TYPES, STATE_NOT_REQUESTED),
+        type(GENERATE_STREAM),
         render_process_id(render_process_id),
         render_view_id(render_view_id),
         security_origin(request_security_origin) {
     DCHECK(requester);
   }
 
   ~DeviceRequest() {}
 
   MediaStreamRequester* requester;
   StreamOptions options;
   std::vector<RequestState> state;
   RequestType type;
   int render_process_id;
   int render_view_id;
   GURL security_origin;
   std::string requested_device_id;
   StreamDeviceInfoArray audio_devices;
   StreamDeviceInfoArray video_devices;
 };
 
+MediaStreamManager::EnumerationCache::EnumerationCache()
+    : valid(false) {
+}
+
 MediaStreamManager::MediaStreamManager(
     AudioInputDeviceManager* audio_input_device_manager,
     VideoCaptureManager* video_capture_manager)
     : ALLOW_THIS_IN_INITIALIZER_LIST(
           device_settings_(new MediaStreamDeviceSettings(this))),
       audio_input_device_manager_(audio_input_device_manager),
       video_capture_manager_(video_capture_manager),
-      enumeration_in_progress_(content::NUM_MEDIA_STREAM_DEVICE_TYPES, false),
+      monitoring_started_(false),
+      enumeration_in_progress_(content::NUM_MEDIA_STREAM_DEVICE_TYPES, 0),
       io_loop_(NULL) {
 }
 
 MediaStreamManager::~MediaStreamManager() {
   DCHECK(requests_.empty());
   DCHECK(!device_thread_.get());
   DCHECK(!io_loop_);
 }
 
 VideoCaptureManager* MediaStreamManager::video_capture_manager() {
@@ skipping 17 matching lines @@
                                         const GURL& security_origin,
                                         std::string* label) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   // Create a new request based on options.
   DeviceRequest new_request(requester, options,
                             render_process_id,
                             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) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   DeviceRequests::iterator it = requests_.begin();
   while (it != requests_.end()) {
     if (it->second.requester == requester && !RequestDone(it->second)) {
       // The request isn't complete, but there might be some devices already
       // opened -> close them.
       DeviceRequest* request = &(it->second);
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE] ==
-          DeviceRequest::kOpening) {
+          DeviceRequest::STATE_OPENING) {
         for (StreamDeviceInfoArray::iterator it =
              request->audio_devices.begin(); it != request->audio_devices.end();
              ++it) {
           audio_input_device_manager()->Close(it->session_id);
         }
       }
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE] ==
-          DeviceRequest::kOpening) {
+          DeviceRequest::STATE_OPENING) {
         for (StreamDeviceInfoArray::iterator it =
              request->video_devices.begin(); it != request->video_devices.end();
              ++it) {
           video_capture_manager()->Close(it->session_id);
         }
       }
       requests_.erase(it++);
     } else {
       ++it;
     }
   }
 }
 
 void MediaStreamManager::CancelGenerateStream(const std::string& label) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   DeviceRequests::iterator it = requests_.find(label);
   if (it != requests_.end()) {
     // The request isn't complete.
     if (!RequestDone(it->second)) {
       DeviceRequest* request = &(it->second);
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE] ==
-          DeviceRequest::kOpening) {
+          DeviceRequest::STATE_OPENING) {
         for (StreamDeviceInfoArray::iterator it =
              request->audio_devices.begin(); it != request->audio_devices.end();
              ++it) {
           audio_input_device_manager()->Close(it->session_id);
         }
       }
       if (request->state[content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE] ==
-          DeviceRequest::kOpening) {
+          DeviceRequest::STATE_OPENING) {
         for (StreamDeviceInfoArray::iterator it =
              request->video_devices.begin(); it != request->video_devices.end();
              ++it) {
           video_capture_manager()->Close(it->session_id);
         }
       }
       requests_.erase(it);
     } else {
       StopGeneratedStream(label);
     }
     device_settings_->RemovePendingCaptureRequest(label);
   }
 }
 
 void MediaStreamManager::StopGeneratedStream(const std::string& label) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   // 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) {
       audio_input_device_manager()->Close(audio_it->session_id);
     }
     for (StreamDeviceInfoArray::iterator video_it =
          it->second.video_devices.begin();
          video_it != it->second.video_devices.end(); ++video_it) {
       video_capture_manager()->Close(video_it->session_id);
     }
-    if (it->second.type == DeviceRequest::kGenerateStream) {
+    if (it->second.type == DeviceRequest::GENERATE_STREAM) {
       NotifyObserverDevicesClosed(&(it->second));
     }
     requests_.erase(it);
-    return;
   }
 }
 
 void MediaStreamManager::EnumerateDevices(
     MediaStreamRequester* requester,
     int render_process_id,
     int render_view_id,
     MediaStreamType type,
     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;
-  if (type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE)
+  EnumerationCache* cache = NULL;
+  if (type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE) {
     options.audio = true;
-  else
+    cache = &audio_enumeration_cache_;
+  } 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::kEnumerateDevices;
+  new_request.type = DeviceRequest::ENUMERATE_DEVICES;
 
-  StartEnumeration(&new_request, label);
+  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));
+
+  DeviceRequests::iterator it = requests_.find(label);
+  if (it != requests_.end()) {
+    DCHECK_EQ(it->second.type, DeviceRequest::ENUMERATE_DEVICES);
+    requests_.erase(it);
+    if (!HasEnumerationRequest()) {
+      StopMonitoring();
+    }
+  }
 }
 
 void MediaStreamManager::OpenDevice(
     MediaStreamRequester* requester,
     int render_process_id,
     int render_view_id,
     const std::string& device_id,
     MediaStreamType type,
     const GURL& security_origin,
     std::string* label) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   // Create a new request.
   StreamOptions options;
   if (type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE)
     options.audio = true;
   else
     options.video = true;
 
   DeviceRequest new_request(requester, options,
                             render_process_id,
                             render_view_id,
                             security_origin);
-  new_request.type = DeviceRequest::kOpenDevice;
+  new_request.type = DeviceRequest::OPEN_DEVICE;
   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) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 
   MediaStreamType stream_type = content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE;
   if (Requested(new_request->options, stream_type)) {
-    new_request->state[stream_type] = DeviceRequest::kRequested;
+    new_request->state[stream_type] = DeviceRequest::STATE_REQUESTED;
+    DCHECK_GE(enumeration_in_progress_[stream_type], 0);
     if (!enumeration_in_progress_[stream_type]) {
-      enumeration_in_progress_[stream_type] = true;
+      enumeration_in_progress_[stream_type]++;

[tommi (sloooow) - chröme, 2012/08/01 10:21:38]

nit: we tend do use prefix increment to avoid a temporary.

[wjia(left Chromium), 2012/08/01 14:24:03]

Done.

       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::kRequested;
+    new_request->state[stream_type] = DeviceRequest::STATE_REQUESTED;
+    DCHECK_GE(enumeration_in_progress_[stream_type], 0);
     if (!enumeration_in_progress_[stream_type]) {
-      enumeration_in_progress_[stream_type] = true;
+      enumeration_in_progress_[stream_type]++;
       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 {
     request_label = RandomLabel();
   } while (requests_.find(request_label) != requests_.end());
 
   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;
 }
 
 void MediaStreamManager::EnsureDeviceThreadAndListener() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   if (device_thread_.get())
     return;
 
   device_thread_.reset(new DeviceThread("MediaStreamDeviceThread"));
   CHECK(device_thread_->Start());
@@ skipping 35 matching lines @@
         request = &(request_it->second);
         break;
       }
     }
   }
   if (request == NULL) {
     // The request doesn't exist.
     return;
   }
 
-  DCHECK_NE(request->state[stream_type], DeviceRequest::kRequested);
+  DCHECK_NE(request->state[stream_type], DeviceRequest::STATE_REQUESTED);
 
   // Check if all devices for this stream type are opened. Update the state if
   // they are.
   for (StreamDeviceInfoArray::iterator device_it = devices->begin();
        device_it != devices->end(); ++device_it) {
     if (device_it->in_use == false) {
       // Wait for more devices to be opened before we're done.
       return;
     }
   }
-  request->state[stream_type] = DeviceRequest::kDone;
+  request->state[stream_type] = DeviceRequest::STATE_DONE;
 
   if (!RequestDone(*request)) {
     // This stream_type is done, but not the other type.
     return;
   }
 
   switch (request->type) {
-    case DeviceRequest::kOpenDevice:
+    case DeviceRequest::OPEN_DEVICE:
       request->requester->DeviceOpened(label, (*devices)[0]);
       break;
-    case DeviceRequest::kGenerateStream:
+    case DeviceRequest::GENERATE_STREAM:
       request->requester->StreamGenerated(label, request->audio_devices,
                                           request->video_devices);
       NotifyObserverDevicesOpened(request);
       break;
     default:
       NOTREACHED();
   }
 }
 
 void MediaStreamManager::Closed(MediaStreamType stream_type,
                                 int capture_session_id) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
 }
 
 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 || cache->devices != devices)) {
+    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
   // back from device_settings that will need to iterate through devices.
   std::list<std::string> label_list;
   for (DeviceRequests::iterator it = requests_.begin(); it != requests_.end();
        ++it) {
-    if (it->second.state[stream_type] == DeviceRequest::kRequested &&
+    if (it->second.state[stream_type] == DeviceRequest::STATE_REQUESTED &&
         Requested(it->second.options, stream_type)) {
-      it->second.state[stream_type] = DeviceRequest::kPendingApproval;
+      if (it->second.type != DeviceRequest::ENUMERATE_DEVICES)
+        it->second.state[stream_type] = DeviceRequest::STATE_PENDING_APPROVAL;
       label_list.push_back(it->first);
     }
   }
   for (std::list<std::string>::iterator it = label_list.begin();
        it != label_list.end(); ++it) {
     DeviceRequest& request = requests_[*it];
     switch (request.type) {
-      case DeviceRequest::kEnumerateDevices:
-        request.requester->DevicesEnumerated(*it, devices);
-        requests_.erase(*it);
+      case DeviceRequest::ENUMERATE_DEVICES:
+        if (need_update_clients)
+          request.requester->DevicesEnumerated(*it, devices);
         break;
-      case DeviceRequest::kOpenDevice:
+      case DeviceRequest::OPEN_DEVICE:
         for (StreamDeviceInfoArray::const_iterator device_it = devices.begin();
              device_it != devices.end(); device_it++) {
           if (request.requested_device_id == device_it->device_id) {
             StreamDeviceInfo device = *device_it;
             device.in_use = false;
             device.session_id =
                 GetDeviceManager(device_it->stream_type)->Open(device);
-            request.state[device_it->stream_type] = DeviceRequest::kOpening;
+            request.state[device_it->stream_type] =
+                DeviceRequest::STATE_OPENING;
             if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE)
               request.audio_devices.push_back(device);
             else
               request.video_devices.push_back(device);
             break;
           }
         }
         break;
       default:
         BrowserThread::PostTask(BrowserThread::IO,
             FROM_HERE,
             base::Bind(&MediaStreamDeviceSettings::AvailableDevices,
                        base::Unretained(device_settings_.get()),
                        *it, stream_type, devices));
     }
   }
   label_list.clear();
-  enumeration_in_progress_[stream_type] = false;
+  enumeration_in_progress_[stream_type]--;

[tommi (sloooow) - chröme, 2012/08/01 10:21:38]

nit: prefix

[wjia(left Chromium), 2012/08/01 14:24:03]

Done.

+  DCHECK_GE(enumeration_in_progress_[stream_type], 0);
 }
 
 void MediaStreamManager::Error(MediaStreamType stream_type,
                                int capture_session_id,
                                MediaStreamProviderError error) {
   // Find the device for the error call.
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   for (DeviceRequests::iterator it = requests_.begin(); it != requests_.end();
        ++it) {
     StreamDeviceInfoArray* devices = NULL;
     if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE) {
       devices = &(it->second.audio_devices);
     } else if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE) {
       devices = &(it->second.video_devices);
     } else {
       NOTREACHED();
     }
 
     int device_idx = 0;
     for (StreamDeviceInfoArray::iterator device_it = devices->begin();
          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::kDone) {
+        if (it->second.state[stream_type] == DeviceRequest::STATE_DONE) {
           // 1. Already opened -> signal device failure and close device.
           //    Use device_idx to signal which of the devices encountered an
           //    error.
           if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE) {
             it->second.requester->AudioDeviceFailed(it->first, device_idx);
           } else if (stream_type ==
                      content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE) {
             it->second.requester->VideoDeviceFailed(it->first, device_idx);
           }
           GetDeviceManager(stream_type)->Close(capture_session_id);
@@ skipping 29 matching lines @@
 
     // Loop through all device types for this request.
     for (StreamDeviceInfoArray::const_iterator device_it = devices.begin();
          device_it != devices.end(); ++device_it) {
       StreamDeviceInfo device_info = *device_it;
 
       // Set in_use to false to be able to track if this device has been
       // 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::kPendingApproval);
+                DeviceRequest::STATE_PENDING_APPROVAL);
       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::kOpening;
+          DeviceRequest::STATE_OPENING;
       if (device_info.stream_type ==
           content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE) {
         request_it->second.audio_devices.push_back(device_info);
       } else if (device_info.stream_type ==
                  content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE) {
         request_it->second.video_devices.push_back(device_info);
       } else {
         NOTREACHED();
       }
     }
     // Check if we received all stream types requested.
     MediaStreamType stream_type =
         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::kError;
+      request_it->second.state[stream_type] = DeviceRequest::STATE_ERROR;
     }
     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::kError;
+      request_it->second.state[stream_type] = DeviceRequest::STATE_ERROR;
     }
     return;
   }
 }
 
 void MediaStreamManager::SettingsError(const std::string& label) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   // Erase this request and report an error.
   DeviceRequests::iterator it = requests_.find(label);
   if (it != requests_.end()) {
-    DCHECK_EQ(it->second.type, DeviceRequest::kGenerateStream);
+    DCHECK_EQ(it->second.type, DeviceRequest::GENERATE_STREAM);
     it->second.requester->StreamGenerationFailed(label);
     requests_.erase(it);
     return;
   }
 }
 
 void MediaStreamManager::UseFakeDevice() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   video_capture_manager()->UseFakeDevice();
   device_settings_->UseFakeUI();
 }
 
 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();
   }
 
   audio_input_device_manager_ = NULL;
   video_capture_manager_ = NULL;
   io_loop_ = NULL;
   device_settings_.reset();
 }
@@ skipping 72 matching lines @@
     MediaStreamType stream_type) {
   if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE) {
     return video_capture_manager();
   } else if (stream_type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE) {
     return audio_input_device_manager();
   }
   NOTREACHED();
   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);
+  } else {
+    // Always do enumeration even though some enumeration is in progress,
+    // because those enumeration commands could be sent before this devices
+    // change.

[tommi (sloooow) - chröme, 2012/08/01 10:21:38]

this makes sense... should we cancel the previous enumerations?

[wjia(left Chromium), 2012/08/01 14:24:03]

In current API between MSM and VCM/AIDM, we are not able to cancel previous
enumerations. If each enumeration has an ID, then we can skip those previous
enumerations when MSM receives OnDevicesEnumerated().

Anyhow, it's ok to keep those previous enumerations for now.  I don't see it
would create confusion for clients. If it does, we can refactor later.

+    enumeration_in_progress_[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