1 files changed, 11 insertions, 0 deletions
diff --git a/dom/cache/StreamList.cpp b/dom/cache/StreamList.cpp
index b72b7f95d5..cbce695b60 100644
--- a/dom/cache/StreamList.cpp
+++ b/dom/cache/StreamList.cpp
@@ -85,6 +85,12 @@ void StreamList::Add(const nsID& aId, nsCOMPtr<nsIInputStream>&& aStream) {
   // All streams should be added on IO thread before we set the stream
   // control on the owning IPC thread.
   MOZ_DIAGNOSTIC_ASSERT(!mStreamControl);
+
+  // Removal of the stream will be triggered when the stream is closed,
+  // which happens only once, so let's ensure nobody adds us twice.
+  MOZ_ASSERT_DEBUG_OR_FUZZING(
+      std::find_if(mList.begin(), mList.end(), MatchById(aId)) == mList.end());
+
   mList.EmplaceBack(aId, std::move(aStream));
 }
 
@@ -93,6 +99,9 @@ already_AddRefed<nsIInputStream> StreamList::Extract(const nsID& aId) {
 
   const auto it = std::find_if(mList.begin(), mList.end(), MatchById(aId));
 
+  // Note that if the stream has not been opened with OpenMode::Eager we will
+  // find it nullptr here and it will have to be opened by the consumer.
+
   return it != mList.end() ? it->mStream.forget() : nullptr;
 }
 
@@ -101,6 +110,7 @@ void StreamList::NoteClosed(const nsID& aId) {
 
   const auto it = std::find_if(mList.begin(), mList.end(), MatchById(aId));
   if (it != mList.end()) {
+    MOZ_ASSERT(!it->mStream, "We expect to find mStream already extracted.");
     mList.RemoveElementAt(it);
     mManager->ReleaseBodyId(aId);
   }
@@ -124,6 +134,7 @@ void StreamList::NoteClosedAll() {
 
 void StreamList::CloseAll() {
   NS_ASSERT_OWNINGTHREAD(StreamList);
+
   if (mStreamControl && mStreamControl->CanSend()) {
     auto* streamControl = std::exchange(mStreamControl, nullptr);