Change RtpHeaderExtension URI to numerical ID.

explainer-use-case-1.md

@@ -65,7 +65,7 @@ interface RtpPacket {
 
 interface RtpHeaderExtension {
   constructor(required RtpHeaderExtensionInit);
-  readonly attribute DOMString uri;
+  readonly attribute octet id;
   readonly attribute ArrayBuffer value;
 }
 
@@ -84,7 +84,7 @@ dictionary RtpPacketInit {
 }
 
 dictionary RtpHeaderExtensionInit {
-  required DOMString uri;
+  required octet id;
   required ArrayBuffer value;
 }