Bug 1838984 - Add Serializable to EncodedVideoChunk r=emilio

This patch add Serializable to EncodedVideoChunk interface with some
dummy functions to make it buildable. The (de-)serialization function
will be implemented in the following patches.

Differential Revision: https://phabricator.services.mozilla.com/D182844

dom/base/StructuredCloneTags.h

@@ -155,6 +155,8 @@ enum StructuredCloneTags : uint32_t {
 
   SCTAG_DOM_VIDEOFRAME,
 
+  SCTAG_DOM_ENCODEDVIDEOCHUNK,
+
   // IMPORTANT: If you plan to add an new IDB tag, it _must_ be add before the
   // "less stable" tags!
 };

dom/media/webcodecs/EncodedVideoChunk.cpp

@@ -160,6 +160,20 @@ uint8_t* EncodedVideoChunk::Data() {
   return mBuffer->Data();
 }
 
+// https://w3c.github.io/webcodecs/#ref-for-deserialization-steps%E2%91%A0
+/* static */
+already_AddRefed<EncodedVideoChunk> EncodedVideoChunk::ReadStructuredClone(
+    JSContext* aCx, nsIGlobalObject* aGlobal,
+    JSStructuredCloneReader* aReader) {
+  return nullptr;
+}
+
+// https://w3c.github.io/webcodecs/#ref-for-serialization-steps%E2%91%A0
+bool EncodedVideoChunk::WriteStructuredClone(
+    JSContext* aCx, JSStructuredCloneWriter* aWriter) const {
+  return false;
+}
+
 #undef LOGW
 #undef LOG_INTERNAL
 

dom/media/webcodecs/EncodedVideoChunk.h

@@ -73,6 +73,13 @@ class EncodedVideoChunk final : public nsISupports, public nsWrapperCache {
   // Non-webidl method.
   uint8_t* Data();
 
+  // [Serializable] implementations: {Read, Write}StructuredClone
+  static already_AddRefed<EncodedVideoChunk> ReadStructuredClone(
+      JSContext* aCx, nsIGlobalObject* aGlobal,
+      JSStructuredCloneReader* aReader);
+  bool WriteStructuredClone(JSContext* aCx,
+                            JSStructuredCloneWriter* aWriter) const;
+
  private:
   // EncodedVideoChunk can run on either main thread or worker thread.
   void AssertIsOnOwningThread() const {

dom/webidl/EncodedVideoChunk.webidl

@@ -7,7 +7,7 @@
  * https://w3c.github.io/webcodecs/#encodedvideochunk
  */
 
-[Exposed=(Window,DedicatedWorker), Pref="dom.media.webcodecs.enabled"]
+[Exposed=(Window,DedicatedWorker), Serializable, Pref="dom.media.webcodecs.enabled"]
 interface EncodedVideoChunk {
   [Throws]
   constructor(EncodedVideoChunkInit init);