IDL: make optional arguments (without default) explicit sometimes

Source/modules/mediastream/RTCPeerConnection.idl

Index: Source/modules/mediastream/RTCPeerConnection.idl
diff --git a/Source/modules/mediastream/RTCPeerConnection.idl b/Source/modules/mediastream/RTCPeerConnection.idl
index fa5494606e720f8f19b2043bc0492e96f623dd77..b9199e324f48593ac1d640bcd4ac0780cea48f08 100644
--- a/Source/modules/mediastream/RTCPeerConnection.idl
+++ b/Source/modules/mediastream/RTCPeerConnection.idl
@@ -36,14 +36,14 @@
     NoInterfaceObject,
     RaisesException=Constructor,
 ] interface RTCPeerConnection : EventTarget {
-    [RaisesException] void createOffer(RTCSessionDescriptionCallback successCallback, [Default=Undefined] optional RTCErrorCallback failureCallback, optional Dictionary rtcOfferOptions);
+    [RaisesException] void createOffer(RTCSessionDescriptionCallback successCallback, optional RTCErrorCallback failureCallback, optional Dictionary rtcOfferOptions);
 
-    [RaisesException] void createAnswer(RTCSessionDescriptionCallback successCallback, [Default=Undefined] optional RTCErrorCallback failureCallback, optional Dictionary mediaConstraints);
+    [RaisesException] void createAnswer(RTCSessionDescriptionCallback successCallback, optional RTCErrorCallback failureCallback, optional Dictionary mediaConstraints);
 
-    [RaisesException] void setLocalDescription(RTCSessionDescription description, [Default=Undefined] optional VoidCallback successCallback, [Default=Undefined] optional RTCErrorCallback failureCallback);
+    [RaisesException] void setLocalDescription(RTCSessionDescription description, optional VoidCallback successCallback, optional RTCErrorCallback failureCallback);
     [RaisesException=Getter] readonly attribute RTCSessionDescription localDescription;
 
-    [RaisesException] void setRemoteDescription(RTCSessionDescription description, [Default=Undefined] optional VoidCallback successCallback, [Default=Undefined] optional RTCErrorCallback failureCallback);
+    [RaisesException] void setRemoteDescription(RTCSessionDescription description, optional VoidCallback successCallback, optional RTCErrorCallback failureCallback);
     [RaisesException=Getter] readonly attribute RTCSessionDescription remoteDescription;
 
     readonly attribute DOMString signalingState;
@@ -65,7 +65,7 @@
     [TypeChecking=Interface, RaisesException] void addStream(MediaStream? stream, optional Dictionary mediaConstraints);
     [TypeChecking=Interface, RaisesException] void removeStream(MediaStream? stream);
 
-    void getStats(RTCStatsCallback successCallback, [Default=Undefined] optional MediaStreamTrack selector);
+    void getStats(RTCStatsCallback successCallback, optional MediaStreamTrack selector);
 
     [RaisesException] RTCDataChannel createDataChannel([TreatUndefinedAs=NullString] DOMString? label, optional Dictionary options);