1 files changed, 27 insertions, 0 deletions
diff --git a/dom/media/PrincipalChangeObserver.h b/dom/media/PrincipalChangeObserver.h
new file mode 100644
index 0000000000..e59c7b7492
--- /dev/null
+++ b/dom/media/PrincipalChangeObserver.h
@@ -0,0 +1,27 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_PRINCIPALCHANGEOBSERVER_H_
+#define MOZILLA_PRINCIPALCHANGEOBSERVER_H_
+
+namespace mozilla::dom {
+
+/**
+ * A PrincipalChangeObserver for any type, but originating from DOMMediaStream,
+ * then expanded to MediaStreamTrack.
+ *
+ * Used to learn about dynamic changes to an object's principal.
+ * Operations relating to these observers must be confined to the main thread.
+ */
+template <typename T>
+class PrincipalChangeObserver {
+ public:
+  virtual void PrincipalChanged(T* aArg) = 0;
+};
+
+}  // namespace mozilla::dom
+
+#endif /* MOZILLA_PRINCIPALCHANGEOBSERVER_H_ */