refactor EnumerateDevices to make it a persistent request.

content/renderer/media/media_stream_dispatcher.cc

Index: content/renderer/media/media_stream_dispatcher.cc
===================================================================
--- content/renderer/media/media_stream_dispatcher.cc	(revision 150440)
+++ content/renderer/media/media_stream_dispatcher.cc	(working copy)
@@ -31,8 +31,36 @@
   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) {
 }
 
@@ -43,6 +71,7 @@
     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_));
@@ -53,6 +82,7 @@
 }
 
 void MediaStreamDispatcher::CancelGenerateStream(int request_id) {
+  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::CancelGenerateStream"
            << ", {request_id = " << request_id << "}";
 
@@ -69,6 +99,7 @@
 }
 
 void MediaStreamDispatcher::StopStream(const std::string& label) {
+  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::StopStream"
            << ", {label = " << label << "}";
 
@@ -85,22 +116,73 @@
     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 << ")";
 
-  requests_.push_back(Request(event_handler, request_id, next_ipc_id_));
-  Send(new MediaStreamHostMsg_EnumerateDevices(routing_id(),
-                                               next_ipc_id_++,
-                                               type,
-                                               security_origin));
+  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;
+    }
+  }
+}
+
 void MediaStreamDispatcher::OpenDevice(
     int request_id,
     const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler,
     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_));
@@ -112,6 +194,7 @@
 }
 
 void MediaStreamDispatcher::CloseDevice(const std::string& label) {
+  DCHECK(main_loop_->BelongsToCurrentThread());
   DVLOG(1) << "MediaStreamDispatcher::CloseDevice"
            << ", {label = " << label << "}";
 
@@ -147,6 +230,7 @@
     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) {
@@ -170,6 +254,7 @@
 }
 
 void MediaStreamDispatcher::OnStreamGenerationFailed(int request_id) {
+  DCHECK(main_loop_->BelongsToCurrentThread());
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
     Request& request = *it;
@@ -187,6 +272,7 @@
 
 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;
@@ -202,6 +288,7 @@
 
 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;
@@ -217,24 +304,41 @@
 
 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);
 
-  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;
+  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 << ")";
     }
   }
 }
 
 void MediaStreamDispatcher::OnDevicesEnumerationFailed(int request_id) {
+  DCHECK(main_loop_->BelongsToCurrentThread());
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
     Request& request = *it;
@@ -254,6 +358,7 @@
     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;
@@ -280,6 +385,7 @@
 }
 
 void MediaStreamDispatcher::OnDeviceOpenFailed(int request_id) {
+  DCHECK(main_loop_->BelongsToCurrentThread());
   for (RequestList::iterator it = requests_.begin();
        it != requests_.end(); ++it) {
     Request& request = *it;