[Mojo Video Capture] Retire buffers when Android Chromium goes to the background

content/browser/renderer_host/media/video_capture_controller.cc

Index: content/browser/renderer_host/media/video_capture_controller.cc
diff --git a/content/browser/renderer_host/media/video_capture_controller.cc b/content/browser/renderer_host/media/video_capture_controller.cc
index 9902d94dad4e4b80de214b7b342299a6720d697c..28c900f3d06a045050029861b9a4eb7485e7f787 100644
--- a/content/browser/renderer_host/media/video_capture_controller.cc
+++ b/content/browser/renderer_host/media/video_capture_controller.cc
@@ -110,6 +110,9 @@ VideoCaptureController::BufferState::~BufferState() = default;
 VideoCaptureController::BufferState::BufferState(
     const VideoCaptureController::BufferState& other) = default;
 
+VideoCaptureController::BufferState& VideoCaptureController::BufferState::
+operator=(const BufferState& other) = default;
+
 void VideoCaptureController::BufferState::RecordConsumerUtilization(
     double utilization) {
   if (std::isfinite(utilization) && utilization >= 0.0) {
@@ -178,8 +181,8 @@ void VideoCaptureController::SetFrameBufferPool(
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   frame_buffer_pool_ = std::move(frame_buffer_pool);
   // Update existing BufferState entries.
-  for (auto& entry : buffer_id_to_state_map_)
-    entry.second.SetFrameBufferPool(frame_buffer_pool_.get());
+  for (auto& entry : buffer_states_)
+    entry.SetFrameBufferPool(frame_buffer_pool_.get());
 }
 
 void VideoCaptureController::SetConsumerFeedbackObserver(
@@ -188,8 +191,8 @@ void VideoCaptureController::SetConsumerFeedbackObserver(
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   consumer_feedback_observer_ = std::move(consumer_feedback_observer);
   // Update existing BufferState entries.
-  for (auto& entry : buffer_id_to_state_map_)
-    entry.second.SetConsumerFeedbackObserver(consumer_feedback_observer_.get());
+  for (auto& entry : buffer_states_)
+    entry.SetConsumerFeedbackObserver(consumer_feedback_observer_.get());
 }
 
 void VideoCaptureController::AddClient(
@@ -251,9 +254,11 @@ int VideoCaptureController::RemoveClient(
   if (!client)
     return kInvalidMediaCaptureSessionId;
 
-  // Take back all buffers held by the |client|.
-  for (const auto& buffer_id : client->buffers_in_use)
-    buffer_id_to_state_map_.at(buffer_id).DecreaseConsumerCount();
+  for (const auto& buffer_id : client->buffers_in_use) {
+    OnClientFinishedConsumingBuffer(
+        client, buffer_id,
+        media::VideoFrameConsumerFeedbackObserver::kNoUtilizationRecorded);
+  }
   client->buffers_in_use.clear();
 
   int session_id = client->session_id;
@@ -356,11 +361,10 @@ void VideoCaptureController::ReturnBuffer(
     NOTREACHED();
     return;
   }
-
-  BufferState& buffer_state = buffer_id_to_state_map_.at(buffer_id);
-  buffer_state.RecordConsumerUtilization(consumer_resource_utilization);
-  buffer_state.DecreaseConsumerCount();
   client->buffers_in_use.erase(buffers_in_use_entry_iter);
+
+  OnClientFinishedConsumingBuffer(client, buffer_id,
+                                  consumer_resource_utilization);
 }
 
 const media::VideoCaptureFormat&
@@ -375,17 +379,14 @@ void VideoCaptureController::OnIncomingCapturedVideoFrame(
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   const int buffer_id = buffer.id();
   DCHECK_NE(buffer_id, media::VideoCaptureBufferPool::kInvalidId);
-
-  // Insert if not exists.
-  const auto it =
-      buffer_id_to_state_map_
-          .insert(std::make_pair(
-              buffer_id, BufferState(buffer_id, buffer.frame_feedback_id(),
-                                     consumer_feedback_observer_.get(),
-                                     frame_buffer_pool_.get())))
-          .first;
-  BufferState& buffer_state = it->second;
-  DCHECK(buffer_state.HasZeroConsumerHoldCount());
+  auto buffer_state_iter = FindBufferState(buffer_id);
+  if (buffer_state_iter == buffer_states_.end()) {
+    buffer_states_.emplace_back(buffer_id, buffer.frame_feedback_id(),
+                                consumer_feedback_observer_.get(),
+                                frame_buffer_pool_.get());
+    buffer_state_iter = buffer_states_.end() - 1;
+  }
+  DCHECK(buffer_state_iter->HasZeroConsumerHoldCount());
 
   if (state_ == VIDEO_CAPTURE_STATE_STARTED) {
     if (!frame->metadata()->HasKey(VideoFrameMetadata::FRAME_RATE)) {
@@ -440,7 +441,7 @@ void VideoCaptureController::OnIncomingCapturedVideoFrame(
         client->buffers_in_use.push_back(buffer_id);
       else
         DCHECK(false) << "Unexpected duplicate buffer: " << buffer_id;
-      buffer_state.IncreaseConsumerCount();
+      buffer_state_iter->IncreaseConsumerCount();
     }
   }
 
@@ -468,7 +469,7 @@ void VideoCaptureController::OnError() {
 
   for (const auto& client : controller_clients_) {
     if (client->session_closed)
-       continue;
+      continue;
     client->event_handler->OnError(client->controller_id);
   }
 }
@@ -478,24 +479,19 @@ void VideoCaptureController::OnLog(const std::string& message) {
   MediaStreamManager::SendMessageToNativeLog("Video capture: " + message);
 }
 
-void VideoCaptureController::OnBufferDestroyed(int buffer_id_to_drop) {
+void VideoCaptureController::OnBufferRetired(int buffer_id) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 
-  for (const auto& client : controller_clients_) {
-    if (client->session_closed)
-      continue;
-
-    auto known_buffers_entry_iter =
-        std::find(std::begin(client->known_buffers),
-                  std::end(client->known_buffers), buffer_id_to_drop);
-    if (known_buffers_entry_iter != std::end(client->known_buffers)) {
-      client->known_buffers.erase(known_buffers_entry_iter);
-      client->event_handler->OnBufferDestroyed(client->controller_id,
-                                               buffer_id_to_drop);
-    }
-  }
+  auto buffer_state_iter = FindBufferState(buffer_id);
+  DCHECK(buffer_state_iter != buffer_states_.end());
 
-  buffer_id_to_state_map_.erase(buffer_id_to_drop);
+  // If there are any clients still using the buffer, we need to allow them
+  // to finish up. We need to hold on to the BufferState entry until then,
+  // because it contains the consumer hold.
+  if (buffer_state_iter->HasZeroConsumerHoldCount())
+    ReleaseBufferState(buffer_state_iter);
+  else
+    buffer_state_iter->set_is_retired();
 }
 
 VideoCaptureController::ControllerClient* VideoCaptureController::FindClient(
@@ -519,4 +515,47 @@ VideoCaptureController::ControllerClient* VideoCaptureController::FindClient(
   return nullptr;
 }
 
+std::vector<VideoCaptureController::BufferState>::iterator
+VideoCaptureController::FindBufferState(int buffer_id) {
+  auto buffer_state_iter =
+      std::find_if(buffer_states_.begin(), buffer_states_.end(),
+                   [buffer_id](const BufferState& entry) {
+                     return entry.buffer_id() == buffer_id;
+                   });
+  return buffer_state_iter;
+}
+
+void VideoCaptureController::OnClientFinishedConsumingBuffer(
+    ControllerClient* client,
+    int buffer_id,
+    double consumer_resource_utilization) {
+  auto buffer_state_iter = FindBufferState(buffer_id);
+  DCHECK(buffer_state_iter != buffer_states_.end());
+
+  buffer_state_iter->RecordConsumerUtilization(consumer_resource_utilization);
+  buffer_state_iter->DecreaseConsumerCount();
+  if (buffer_state_iter->HasZeroConsumerHoldCount() &&
+      buffer_state_iter->is_retired()) {
+    ReleaseBufferState(buffer_state_iter);
+  }
+}
+
+void VideoCaptureController::ReleaseBufferState(
+    const std::vector<BufferState>::iterator& buffer_state_iter) {
+  for (const auto& client : controller_clients_) {
+    if (client->session_closed)
+      continue;
+
+    auto known_buffers_entry_iter = std::find(std::begin(client->known_buffers),
+                                              std::end(client->known_buffers),
+                                              buffer_state_iter->buffer_id());
+    if (known_buffers_entry_iter != std::end(client->known_buffers)) {
+      client->known_buffers.erase(known_buffers_entry_iter);
+      client->event_handler->OnBufferDestroyed(client->controller_id,
+                                               buffer_state_iter->buffer_id());
+    }
+  }
+  buffer_states_.erase(buffer_state_iter);
+}
+
 }  // namespace content