Update interfaces/media-capabilities.idl (#27651)

diff --git a/interfaces/media-capabilities.idl b/interfaces/media-capabilities.idl
index fb52b7c..128d010 100644
--- a/interfaces/media-capabilities.idl
+++ b/interfaces/media-capabilities.idl
@@ -20,11 +20,12 @@
 enum MediaDecodingType {
   "file",
   "media-source",
+  "webrtc"
 };
 
 enum MediaEncodingType {
   "record",
-  "transmission"
+  "webrtc"
 };
 
 dictionary VideoConfiguration {
@@ -37,6 +38,7 @@
   HdrMetadataType hdrMetadataType;
   ColorGamut colorGamut;
   TransferFunction transferFunction;
+  DOMString scalabilityMode;
 };
 
 enum HdrMetadataType {