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 148913)
+++ content/renderer/media/media_stream_dispatcher.cc	(working copy)
@@ -31,6 +31,19 @@
   media_stream::StreamDeviceInfoArray video_array;
 };
 
+MediaStreamDispatcher::EnumerationRequest::EnumerationRequest(
+    const base::WeakPtr<MediaStreamDispatcherEventHandler>& handler,
+    int request_id)
+    : handler(handler),
+      request_id(request_id) {
+}
+
+MediaStreamDispatcher::EnumerationState::EnumerationState()
+    : started(false),
+      ipc_id(0),
+      cache_valid(false) {
+}
+
 MediaStreamDispatcher::MediaStreamDispatcher(RenderViewImpl* render_view)
     : content::RenderViewObserver(render_view),
       next_ipc_id_(0) {
@@ -88,13 +101,63 @@
   DVLOG(1) << "MediaStreamDispatcher::EnumerateDevices("

[tommi (sloooow) - chröme, 2012/07/30 12:10:21]

Is this method (and the other methods that touch the unprotected member
variables) always called on a known thread?  If so, can we DCHECK that?

[wjia(left Chromium), 2012/08/01 01:28:59]

They are all called on main thread. DCHECK has been added.

            << 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));
+  DCHECK(type == content::MEDIA_STREAM_DEVICE_TYPE_AUDIO_CAPTURE ||
+         type == content::MEDIA_STREAM_DEVICE_TYPE_VIDEO_CAPTURE);
+
+  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->cache_valid) {
+    event_handler->OnDevicesEnumerated(request_id, state->cached_device);
+  } else if (!state->started) {
+    state->started = true;
+    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) {
+  DVLOG(1) << "MediaStreamDispatcher::StopEnumerateDevices("
+           << request_id << ")";
+
+  // Just need remove the request from one type.
+  RemoveEnumerationRequest(request_id, event_handler,
+      &audio_enumeration_state_) ||
+  RemoveEnumerationRequest(request_id, event_handler,
+      &video_enumeration_state_);
+}
+
+bool 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->label.empty()) {
+        // No more request and has a label, try to stop the label
+        // and invalidate the state.
+        Send(new MediaStreamHostMsg_StopGeneratedStream(
+            routing_id(), state->label));
+        state->started = false;
+        state->cache_valid = false;
+      }
+      return true;
+    }
+  }
+  return false;
+}
+
 void MediaStreamDispatcher::OpenDevice(
     int request_id,
     const base::WeakPtr<MediaStreamDispatcherEventHandler>& event_handler,
@@ -217,19 +280,29 @@
 
 void MediaStreamDispatcher::OnDevicesEnumerated(
     int request_id,
+    const std::string& label,
     const media_stream::StreamDeviceInfoArray& device_array) {
+  EnumerationState* state;
+  if (audio_enumeration_state_.started &&
+      request_id == audio_enumeration_state_.ipc_id) {
+    state = &audio_enumeration_state_;
+  } else if (video_enumeration_state_.started &&
+             request_id == video_enumeration_state_.ipc_id) {
+    state = &video_enumeration_state_;
+  } else {
+    return;
+  }
 
-  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;
+  state->label = label;
+  state->cache_valid = true;
+  state->cached_device = 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 << ")";
     }
   }
 }