Add an API for a "keyframe has been requested" event

index.bs

@@ -590,19 +590,35 @@ partial interface DedicatedWorkerGlobalScope {
     attribute EventHandler onrtctransform;
 };
 
-[Exposed=DedicatedWorker]
-interface RTCRtpScriptTransformer {
+interface mixin RTCRtpScriptSource {
     readonly attribute ReadableStream readable;
-    readonly attribute WritableStream writable;
-    readonly attribute any options;
     Promise<unsigned long long> generateKeyFrame(optional DOMString rid);
     Promise<undefined> sendKeyFrameRequest();
 };
 
+interface mixin RTCRtpScriptSink {
+    readonly attribute WritableStream writable;
+    attribute EventHandler onkeyframerequest;
+};
+
+[Exposed=DedicatedWorker]
+interface RTCRtpScriptTransformer {
+    readonly attribute any options;
+};
+
+RTCRtpScriptTransformer includes RTCRtpScriptSource;
+RTCRtpScriptTransformer includes RTCRtpScriptSink;
+
 [Exposed=Window]
 interface RTCRtpScriptTransform {
     constructor(Worker worker, optional any options, optional sequence<object> transfer);
 };
+
+[Exposed=DedicatedWorker]
+interface KeyFrameRequestEvent : Event {
+  constructor(DOMString type, optional DOMString rid);
+  readonly attribute DOMString? rid;
+};
 </pre>
 
 ## Operations ## {#RTCRtpScriptTransform-operations}
@@ -636,12 +652,12 @@ Each RTCRtpScriptTransform has the following set of [$association steps$], given
     1. Set |transformer|.`[[encoder]]` to |encoder|.
     1. Set |transformer|.`[[depacketizer]]` to |depacketizer|.
 
-The <dfn method for="RTCRtpScriptTransformer">generateKeyFrame(|rid|)</dfn> method steps are:
+The <dfn method for="RTCRtpScriptSource">generateKeyFrame(|rid|)</dfn> method steps are:
 1. Let |promise| be a new promise.
 1. Run the [$generate key frame algorithm$] with |promise|, |this|.`[[encoder]]` and |rid|.
 1. Return |promise|.
 
-The <dfn method for="RTCRtpScriptTransformer">sendKeyFrameRequest()</dfn> method steps are:
+The <dfn method for="RTCRtpScriptSource">sendKeyFrameRequest()</dfn> method steps are:
 1. Let |promise| be a new promise.
 1. Run the [$send request key frame algorithm$] with |promise| and |this|.`[[depacketizer]]`.
 1. Return |promise|.
@@ -655,12 +671,22 @@ This allows algorithms to go from an {{RTCRtpScriptTransformer}} object to its {
 The <dfn attribute for="RTCRtpScriptTransformer">options</dfn> getter steps are:
 1. Return [=this=].`[[options]]`.
 
-The <dfn attribute for="RTCRtpScriptTransformer">readable</dfn> getter steps are:
+The <dfn attribute for="RTCRtpScriptSource">readable</dfn> getter steps are:
 1. Return [=this=].`[[readable]]`.
 
-The <dfn attribute for="RTCRtpScriptTransformer">writable</dfn> getter steps are:
+The <dfn attribute for="RTCRtpScriptSink">writable</dfn> getter steps are:
 1. Return [=this=].`[[writable]]`.
 
+The <dfn attribute for="RTCRtpScriptSink">onbandwidthestimate</dfn> EventHandler has type bandwidthestimate.
+
+The <dfn attribute for="RTCRtpScriptSink">onkeyframerequest</dfn> EventHandler has type keyframerequest.
+
+## Events ## {#RTCRtpScriptTransformer-events}
+
+The following events fire on an {{RTCRtpScriptTransformer}}:
+
+* keyframerequest of type {{KeyFrameRequestEvent}} - fired when the sink determines that a key frame has been requested. In the context of {{RTCRtpScriptTransform}}, if the event is not cancelled, the information will be passed to the source as if the generateKeyFrame() function had been called. <!-- NOTE IN DRAFT: generateKeyFrame() and requestKeyFrame() should merge -->
+
 ## KeyFrame Algorithms ## {#KeyFrame-algorithms}
 
 The <dfn abstract-op>generate key frame algorithm</dfn>, given |promise|, |encoder| and |rid|, is defined by running these steps: