Bug 1748644 - MIDI ports should stop responding to parent message once they've been disconnected from the document that owned them r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D135700

dom/midi/MIDIInput.cpp

@@ -37,7 +37,11 @@ JSObject* MIDIInput::WrapObject(JSContext* aCx,
 }
 
 void MIDIInput::Receive(const nsTArray<MIDIMessage>& aMsgs) {
-  nsCOMPtr<Document> doc = GetOwner() ? GetOwner()->GetDoc() : nullptr;
+  if (!GetOwner()) {
+    return;  // Ignore messages once we've been disconnected from the owner
+  }
+
+  nsCOMPtr<Document> doc = GetOwner()->GetDoc();
   if (!doc) {
     NS_WARNING("No document available to send MIDIMessageEvent to!");
     return;

dom/midi/MIDIPort.cpp

@@ -163,6 +163,10 @@ void MIDIPort::Notify(const void_t& aVoid) {
 }
 
 void MIDIPort::FireStateChangeEvent() {
+  if (!GetOwner()) {
+    return;  // Ignore changes once we've been disconnected from the owner
+  }
+
   StateChange();
 
   MOZ_ASSERT(mPort);