Bug 1681801 - move experimental methods of `SourceBuffer` to partial interface. r=bryce,webidl,smaug

It would be good to separate the standard methods and experimental methods for SourceBuffer in order to clearly see what we support in the spec.

Differential Revision: https://phabricator.services.mozilla.com/D99372

dom/webidl/SourceBuffer.webidl

@@ -41,22 +41,25 @@ interface SourceBuffer : EventTarget {
   void appendBuffer(ArrayBuffer data);
   [Throws]
   void appendBuffer(ArrayBufferView data);
-  // Experimental function as proposed in:
-  // https://github.com/w3c/media-source/issues/100 for promise proposal.
-  [Throws, Pref="media.mediasource.experimental.enabled"]
-  Promise<void> appendBufferAsync(ArrayBuffer data);
-  [Throws, Pref="media.mediasource.experimental.enabled"]
-  Promise<void> appendBufferAsync(ArrayBufferView data);
   //[Throws]
   //void appendStream(Stream stream, [EnforceRange] optional unsigned long long maxSize);
   [Throws]
   void abort();
   [Throws]
   void remove(double start, unrestricted double end);
+};
+
+// Mozilla extensions for experimental features
+partial interface SourceBuffer {
   // Experimental function as proposed in:
   // https://github.com/w3c/media-source/issues/100 for promise proposal.
   [Throws, Pref="media.mediasource.experimental.enabled"]
+  Promise<void> appendBufferAsync(ArrayBuffer data);
+  [Throws, Pref="media.mediasource.experimental.enabled"]
+  Promise<void> appendBufferAsync(ArrayBufferView data);
+  [Throws, Pref="media.mediasource.experimental.enabled"]
   Promise<void> removeAsync(double start, unrestricted double end);
+
   // Experimental function as proposed in:
   // https://github.com/w3c/media-source/issues/155
   [Throws]