Auto merge of #23748 - saschanaz:default-dict, r=Manishearth

Sync WebIDL.py with gecko

<!-- Please describe your changes on the following line: -->

The new change requires default dictionary value for optional dictionary-type arguments.

---
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- [ ] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #23703

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- [x] There are tests for these changes

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68 files changed, 90 insertions, 89 deletions

diff --git a/components/script/dom/webidls/AnalyserNode.webidl b/components/script/dom/webidls/AnalyserNode.webidl
index 6747cda0690..07826c16fab 100644
--- a/components/script/dom/webidls/AnalyserNode.webidl
+++ b/components/script/dom/webidls/AnalyserNode.webidl
@@ -14,7 +14,7 @@ dictionary AnalyserOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional AnalyserOptions options)]
+ Constructor (BaseAudioContext context, optional AnalyserOptions options = {})]
 interface AnalyserNode : AudioNode {
   void getFloatFrequencyData (Float32Array array);
   void getByteFrequencyData (Uint8Array array);
diff --git a/components/script/dom/webidls/AudioBufferSourceNode.webidl b/components/script/dom/webidls/AudioBufferSourceNode.webidl
index 929cdc05c1a..da1222a6935 100644
--- a/components/script/dom/webidls/AudioBufferSourceNode.webidl
+++ b/components/script/dom/webidls/AudioBufferSourceNode.webidl
@@ -16,7 +16,7 @@ dictionary AudioBufferSourceOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional AudioBufferSourceOptions options)]
+ Constructor (BaseAudioContext context, optional AudioBufferSourceOptions options = {})]
 interface AudioBufferSourceNode : AudioScheduledSourceNode {
   [Throws] attribute AudioBuffer? buffer;
   readonly attribute AudioParam playbackRate;
diff --git a/components/script/dom/webidls/AudioContext.webidl b/components/script/dom/webidls/AudioContext.webidl
index c47813d21e0..6acf7ec3e7c 100644
--- a/components/script/dom/webidls/AudioContext.webidl
+++ b/components/script/dom/webidls/AudioContext.webidl
@@ -23,7 +23,7 @@ dictionary AudioTimestamp {
 };
 
 [Exposed=Window,
- Constructor(optional AudioContextOptions contextOptions)]
+ Constructor(optional AudioContextOptions contextOptions = {})]
 interface AudioContext : BaseAudioContext {
   readonly attribute double baseLatency;
   readonly attribute double outputLatency;
diff --git a/components/script/dom/webidls/BiquadFilterNode.webidl b/components/script/dom/webidls/BiquadFilterNode.webidl
index e8ddaee1cac..d222e9a7297 100644
--- a/components/script/dom/webidls/BiquadFilterNode.webidl
+++ b/components/script/dom/webidls/BiquadFilterNode.webidl
@@ -26,7 +26,7 @@ dictionary BiquadFilterOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional BiquadFilterOptions options)]
+ Constructor (BaseAudioContext context, optional BiquadFilterOptions options = {})]
 interface BiquadFilterNode : AudioNode {
   attribute BiquadFilterType type;
   readonly attribute AudioParam frequency;
diff --git a/components/script/dom/webidls/Blob.webidl b/components/script/dom/webidls/Blob.webidl
index b06da6d2fae..d58c67a6398 100644
--- a/components/script/dom/webidls/Blob.webidl
+++ b/components/script/dom/webidls/Blob.webidl
@@ -5,7 +5,7 @@
 // https://w3c.github.io/FileAPI/#blob
 
 [Constructor(optional sequence<BlobPart> blobParts,
-  optional BlobPropertyBag options),
+  optional BlobPropertyBag options = {}),
  Exposed=(Window,Worker)]
 interface Blob {
 
diff --git a/components/script/dom/webidls/Bluetooth.webidl b/components/script/dom/webidls/Bluetooth.webidl
index c5ae3f8f26c..4491a296c41 100644
--- a/components/script/dom/webidls/Bluetooth.webidl
+++ b/components/script/dom/webidls/Bluetooth.webidl
@@ -34,7 +34,7 @@ interface Bluetooth : EventTarget {
   // [SecureContext, SameObject]
   // readonly attribute BluetoothDevice? referringDevice;
   [SecureContext]
-  Promise<BluetoothDevice> requestDevice(optional RequestDeviceOptions options);
+  Promise<BluetoothDevice> requestDevice(optional RequestDeviceOptions options = {});
 };
 
 // Bluetooth implements BluetoothDeviceEventHandlers;
diff --git a/components/script/dom/webidls/ChannelMergerNode.webidl b/components/script/dom/webidls/ChannelMergerNode.webidl
index f8345fe4512..33fc0e6ea67 100644
--- a/components/script/dom/webidls/ChannelMergerNode.webidl
+++ b/components/script/dom/webidls/ChannelMergerNode.webidl
@@ -11,6 +11,6 @@ dictionary ChannelMergerOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional ChannelMergerOptions options)]
+ Constructor (BaseAudioContext context, optional ChannelMergerOptions options = {})]
 interface ChannelMergerNode : AudioNode {
 };
diff --git a/components/script/dom/webidls/ChannelSplitterNode.webidl b/components/script/dom/webidls/ChannelSplitterNode.webidl
index 1056fce61bf..d776ac62ac3 100644
--- a/components/script/dom/webidls/ChannelSplitterNode.webidl
+++ b/components/script/dom/webidls/ChannelSplitterNode.webidl
@@ -11,6 +11,6 @@ dictionary ChannelSplitterOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional ChannelSplitterOptions options)]
+ Constructor (BaseAudioContext context, optional ChannelSplitterOptions options = {})]
 interface ChannelSplitterNode : AudioNode {
 };
diff --git a/components/script/dom/webidls/CloseEvent.webidl b/components/script/dom/webidls/CloseEvent.webidl
index f69d08c37a8..a689b337328 100644
--- a/components/script/dom/webidls/CloseEvent.webidl
+++ b/components/script/dom/webidls/CloseEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 //https://html.spec.whatwg.org/multipage/#the-closeevent-interfaces
-[Constructor(DOMString type, optional CloseEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional CloseEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface CloseEvent : Event {
   readonly attribute boolean wasClean;
   readonly attribute unsigned short code;
diff --git a/components/script/dom/webidls/CompositionEvent.webidl b/components/script/dom/webidls/CompositionEvent.webidl
index c018aa6deac..043873c9354 100644
--- a/components/script/dom/webidls/CompositionEvent.webidl
+++ b/components/script/dom/webidls/CompositionEvent.webidl
@@ -8,7 +8,7 @@
  */
 
 // https://w3c.github.io/uievents/#idl-compositionevent
-[Pref="dom.compositionevent.enabled", Constructor(DOMString type, optional CompositionEventInit eventInitDict)]
+[Pref="dom.compositionevent.enabled", Constructor(DOMString type, optional CompositionEventInit eventInitDict = {})]
 interface CompositionEvent : UIEvent {
   readonly attribute DOMString data;
 };
diff --git a/components/script/dom/webidls/CustomElementRegistry.webidl b/components/script/dom/webidls/CustomElementRegistry.webidl
index 1072eed0031..d2ebff0bdf0 100644
--- a/components/script/dom/webidls/CustomElementRegistry.webidl
+++ b/components/script/dom/webidls/CustomElementRegistry.webidl
@@ -6,7 +6,7 @@
 [Pref="dom.customelements.enabled"]
 interface CustomElementRegistry {
   [Throws, CEReactions]
-  void define(DOMString name, CustomElementConstructor constructor_, optional ElementDefinitionOptions options);
+  void define(DOMString name, CustomElementConstructor constructor_, optional ElementDefinitionOptions options = {});
 
   any get(DOMString name);
 
diff --git a/components/script/dom/webidls/CustomEvent.webidl b/components/script/dom/webidls/CustomEvent.webidl
index 2e77d67fe4b..5bede1513f2 100644
--- a/components/script/dom/webidls/CustomEvent.webidl
+++ b/components/script/dom/webidls/CustomEvent.webidl
@@ -13,7 +13,7 @@
  * http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0.
  */
 
-[Constructor(DOMString type, optional CustomEventInit eventInitDict),
+[Constructor(DOMString type, optional CustomEventInit eventInitDict = {}),
  Exposed=(Window,Worker)]
 interface CustomEvent : Event {
   readonly attribute any detail;
diff --git a/components/script/dom/webidls/DOMMatrix.webidl b/components/script/dom/webidls/DOMMatrix.webidl
index d617f20af99..ffaa720b7d9 100644
--- a/components/script/dom/webidls/DOMMatrix.webidl
+++ b/components/script/dom/webidls/DOMMatrix.webidl
@@ -14,7 +14,7 @@
  Exposed=(Window,Worker)]
 interface DOMMatrix : DOMMatrixReadOnly {
 
-    [NewObject, Throws] static DOMMatrix fromMatrix(optional DOMMatrixInit other);
+    [NewObject, Throws] static DOMMatrix fromMatrix(optional DOMMatrixInit other = {});
     [NewObject, Throws] static DOMMatrix fromFloat32Array(Float32Array array32);
     [NewObject, Throws] static DOMMatrix fromFloat64Array(Float64Array array64);
 
@@ -44,8 +44,8 @@ interface DOMMatrix : DOMMatrixReadOnly {
     inherit attribute unrestricted double m44;
 
     // Mutable transform methods
-    [Throws] DOMMatrix multiplySelf(optional DOMMatrixInit other);
-    [Throws] DOMMatrix preMultiplySelf(optional DOMMatrixInit other);
+    [Throws] DOMMatrix multiplySelf(optional DOMMatrixInit other = {});
+    [Throws] DOMMatrix preMultiplySelf(optional DOMMatrixInit other = {});
     DOMMatrix translateSelf(optional unrestricted double tx = 0,
                             optional unrestricted double ty = 0,
                             optional unrestricted double tz = 0);
diff --git a/components/script/dom/webidls/DOMMatrixReadOnly.webidl b/components/script/dom/webidls/DOMMatrixReadOnly.webidl
index eb7051ba529..ea5d8caf8e5 100644
--- a/components/script/dom/webidls/DOMMatrixReadOnly.webidl
+++ b/components/script/dom/webidls/DOMMatrixReadOnly.webidl
@@ -14,7 +14,7 @@
  Exposed=(Window,Worker)]
 interface DOMMatrixReadOnly {
 
-    [NewObject, Throws] static DOMMatrixReadOnly fromMatrix(optional DOMMatrixInit other);
+    [NewObject, Throws] static DOMMatrixReadOnly fromMatrix(optional DOMMatrixInit other = {});
     [NewObject, Throws] static DOMMatrixReadOnly fromFloat32Array(Float32Array array32);
     [NewObject, Throws] static DOMMatrixReadOnly fromFloat64Array(Float64Array array64);
 
@@ -73,12 +73,12 @@ interface DOMMatrixReadOnly {
                               optional unrestricted double angle = 0);
     DOMMatrix skewX(optional unrestricted double sx = 0);
     DOMMatrix skewY(optional unrestricted double sy = 0);
-    [Throws] DOMMatrix multiply(optional DOMMatrixInit other);
+    [Throws] DOMMatrix multiply(optional DOMMatrixInit other = {});
     DOMMatrix flipX();
     DOMMatrix flipY();
     DOMMatrix inverse();
 
-    DOMPoint            transformPoint(optional DOMPointInit point);
+    DOMPoint            transformPoint(optional DOMPointInit point = {});
     Float32Array        toFloat32Array();
     Float64Array        toFloat64Array();
 //                      stringifier;
diff --git a/components/script/dom/webidls/DOMPoint.webidl b/components/script/dom/webidls/DOMPoint.webidl
index 9f75a1c835f..34a355f6085 100644
--- a/components/script/dom/webidls/DOMPoint.webidl
+++ b/components/script/dom/webidls/DOMPoint.webidl
@@ -14,7 +14,7 @@
              optional unrestricted double z = 0, optional unrestricted double w = 1),
  Exposed=(Window,Worker)]
 interface DOMPoint : DOMPointReadOnly {
-    [NewObject] static DOMPoint fromPoint(optional DOMPointInit other = null);
+    [NewObject] static DOMPoint fromPoint(optional DOMPointInit other = {});
 
     inherit attribute unrestricted double x;
     inherit attribute unrestricted double y;
diff --git a/components/script/dom/webidls/DOMPointReadOnly.webidl b/components/script/dom/webidls/DOMPointReadOnly.webidl
index b6478f31337..23643179333 100644
--- a/components/script/dom/webidls/DOMPointReadOnly.webidl
+++ b/components/script/dom/webidls/DOMPointReadOnly.webidl
@@ -14,7 +14,7 @@
              optional unrestricted double z = 0, optional unrestricted double w = 1),
  Exposed=(Window,Worker)]
 interface DOMPointReadOnly {
-    [NewObject] static DOMPointReadOnly fromPoint(optional DOMPointInit other = null);
+    [NewObject] static DOMPointReadOnly fromPoint(optional DOMPointInit other = {});
 
     readonly attribute unrestricted double x;
     readonly attribute unrestricted double y;
diff --git a/components/script/dom/webidls/DOMQuad.webidl b/components/script/dom/webidls/DOMQuad.webidl
index 397118a88aa..8711dd44215 100644
--- a/components/script/dom/webidls/DOMQuad.webidl
+++ b/components/script/dom/webidls/DOMQuad.webidl
@@ -10,12 +10,12 @@
  * related or neighboring rights to this work.
  */
 
-[Constructor(optional DOMPointInit p1, optional DOMPointInit p2,
-             optional DOMPointInit p3, optional DOMPointInit p4),
+[Constructor(optional DOMPointInit p1 = {}, optional DOMPointInit p2 = {},
+             optional DOMPointInit p3 = {}, optional DOMPointInit p4 = {}),
  Exposed=(Window,Worker)]
 interface DOMQuad {
-    [NewObject] static DOMQuad fromRect(optional DOMRectInit other);
-    [NewObject] static DOMQuad fromQuad(optional DOMQuadInit other);
+    [NewObject] static DOMQuad fromRect(optional DOMRectInit other = {});
+    [NewObject] static DOMQuad fromQuad(optional DOMQuadInit other = {});
 
     [SameObject] readonly attribute DOMPoint p1;
     [SameObject] readonly attribute DOMPoint p2;
@@ -25,8 +25,8 @@ interface DOMQuad {
 };
 
 dictionary DOMQuadInit {
-    DOMPointInit p1 = null;
-    DOMPointInit p2 = null;
-    DOMPointInit p3 = null;
-    DOMPointInit p4 = null;
+    DOMPointInit p1 = {};
+    DOMPointInit p2 = {};
+    DOMPointInit p3 = {};
+    DOMPointInit p4 = {};
 };
diff --git a/components/script/dom/webidls/Document.webidl b/components/script/dom/webidls/Document.webidl
index 85c3362f42e..0127f8ecf98 100644
--- a/components/script/dom/webidls/Document.webidl
+++ b/components/script/dom/webidls/Document.webidl
@@ -33,9 +33,9 @@ interface Document : Node {
   HTMLCollection getElementsByClassName(DOMString classNames);
 
   [CEReactions, NewObject, Throws]
-  Element createElement(DOMString localName, optional ElementCreationOptions options);
+  Element createElement(DOMString localName, optional ElementCreationOptions options = {});
   [CEReactions, NewObject, Throws]
-  Element createElementNS(DOMString? namespace, DOMString qualifiedName, optional ElementCreationOptions options);
+  Element createElementNS(DOMString? namespace, DOMString qualifiedName, optional ElementCreationOptions options = {});
   [NewObject]
   DocumentFragment createDocumentFragment();
   [NewObject]
diff --git a/components/script/dom/webidls/Element.webidl b/components/script/dom/webidls/Element.webidl
index af14f81b373..f45dfe53f1a 100644
--- a/components/script/dom/webidls/Element.webidl
+++ b/components/script/dom/webidls/Element.webidl
@@ -91,12 +91,12 @@ partial interface Element {
   [NewObject]
   DOMRect getBoundingClientRect();
 
-  void scroll(optional ScrollToOptions options);
+  void scroll(optional ScrollToOptions options = {});
   void scroll(unrestricted double x, unrestricted double y);
 
-  void scrollTo(optional ScrollToOptions options);
+  void scrollTo(optional ScrollToOptions options = {});
   void scrollTo(unrestricted double x, unrestricted double y);
-  void scrollBy(optional ScrollToOptions options);
+  void scrollBy(optional ScrollToOptions options = {});
   void scrollBy(unrestricted double x, unrestricted double y);
   attribute unrestricted double scrollTop;
   attribute unrestricted double scrollLeft;
diff --git a/components/script/dom/webidls/ErrorEvent.webidl b/components/script/dom/webidls/ErrorEvent.webidl
index 9fb248e6095..165fbd35110 100644
--- a/components/script/dom/webidls/ErrorEvent.webidl
+++ b/components/script/dom/webidls/ErrorEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://html.spec.whatwg.org/multipage/#the-errorevent-interface
 
-[Constructor(DOMString type, optional ErrorEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional ErrorEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface ErrorEvent : Event {
   readonly attribute DOMString message;
   readonly attribute DOMString filename;
diff --git a/components/script/dom/webidls/Event.webidl b/components/script/dom/webidls/Event.webidl
index 2bf103149d9..c688daedb2e 100644
--- a/components/script/dom/webidls/Event.webidl
+++ b/components/script/dom/webidls/Event.webidl
@@ -6,7 +6,7 @@
  * https://dom.spec.whatwg.org/#event
  */
 
-[Constructor(DOMString type, optional EventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional EventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface Event {
   [Pure]
   readonly attribute DOMString type;
diff --git a/components/script/dom/webidls/EventSource.webidl b/components/script/dom/webidls/EventSource.webidl
index d1c33a6c3fc..7784c97d4ca 100644
--- a/components/script/dom/webidls/EventSource.webidl
+++ b/components/script/dom/webidls/EventSource.webidl
@@ -6,7 +6,7 @@
  * https://html.spec.whatwg.org/multipage/#eventsource
  */
 
-[Constructor(DOMString url, optional EventSourceInit eventSourceInitDict),
+[Constructor(DOMString url, optional EventSourceInit eventSourceInitDict = {}),
  Exposed=(Window,Worker)]
 interface EventSource : EventTarget {
   readonly attribute DOMString url;
diff --git a/components/script/dom/webidls/EventTarget.webidl b/components/script/dom/webidls/EventTarget.webidl
index b0a6e77035e..283f86a806f 100644
--- a/components/script/dom/webidls/EventTarget.webidl
+++ b/components/script/dom/webidls/EventTarget.webidl
@@ -10,13 +10,13 @@ interface EventTarget {
   void addEventListener(
     DOMString type,
     EventListener? callback,
-    optional (AddEventListenerOptions or boolean) options
+    optional (AddEventListenerOptions or boolean) options = {}
   );
 
   void removeEventListener(
     DOMString type,
     EventListener? callback,
-    optional (EventListenerOptions or boolean) options
+    optional (EventListenerOptions or boolean) options = {}
   );
 
   [Throws]
diff --git a/components/script/dom/webidls/ExtendableEvent.webidl b/components/script/dom/webidls/ExtendableEvent.webidl
index 7dc2983fe74..5d6c4786c3f 100644
--- a/components/script/dom/webidls/ExtendableEvent.webidl
+++ b/components/script/dom/webidls/ExtendableEvent.webidl
@@ -5,7 +5,7 @@
 // https://w3c.github.io/ServiceWorker/#extendable-event
 
 [Constructor(DOMString type,
- optional ExtendableEventInit eventInitDict),
+ optional ExtendableEventInit eventInitDict = {}),
  Exposed=ServiceWorker,
  Pref="dom.serviceworker.enabled"]
 interface ExtendableEvent : Event {
diff --git a/components/script/dom/webidls/ExtendableMessageEvent.webidl b/components/script/dom/webidls/ExtendableMessageEvent.webidl
index 3b06fb08cd8..e934d06b50b 100644
--- a/components/script/dom/webidls/ExtendableMessageEvent.webidl
+++ b/components/script/dom/webidls/ExtendableMessageEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://w3c.github.io/ServiceWorker/#extendablemessage-event-section
 
-[Constructor(DOMString type, optional ExtendableMessageEventInit eventInitDict),
+[Constructor(DOMString type, optional ExtendableMessageEventInit eventInitDict = {}),
  Exposed=ServiceWorker,
  Pref="dom.serviceworker.enabled"]
 interface ExtendableMessageEvent : ExtendableEvent {
diff --git a/components/script/dom/webidls/Fetch.webidl b/components/script/dom/webidls/Fetch.webidl
index 3b424ba85b6..ad0907d7436 100644
--- a/components/script/dom/webidls/Fetch.webidl
+++ b/components/script/dom/webidls/Fetch.webidl
@@ -7,5 +7,5 @@
 [Exposed=(Window,Worker)]
 
 partial interface WindowOrWorkerGlobalScope {
-  [NewObject] Promise<Response> fetch(RequestInfo input, optional RequestInit init);
+  [NewObject] Promise<Response> fetch(RequestInfo input, optional RequestInit init = {});
 };
diff --git a/components/script/dom/webidls/File.webidl b/components/script/dom/webidls/File.webidl
index 00e1709ecc1..04e670723e4 100644
--- a/components/script/dom/webidls/File.webidl
+++ b/components/script/dom/webidls/File.webidl
@@ -6,7 +6,7 @@
 
 [Constructor(sequence<BlobPart> fileBits,
             DOMString fileName,
-            optional FilePropertyBag options),
+            optional FilePropertyBag options = {}),
  Exposed=(Window,Worker)]
 interface File : Blob {
   readonly attribute DOMString name;
diff --git a/components/script/dom/webidls/FocusEvent.webidl b/components/script/dom/webidls/FocusEvent.webidl
index 5371399228f..67dec33a952 100644
--- a/components/script/dom/webidls/FocusEvent.webidl
+++ b/components/script/dom/webidls/FocusEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-FocusEvent
-[Constructor(DOMString typeArg, optional FocusEventInit focusEventInitDict),
+[Constructor(DOMString typeArg, optional FocusEventInit focusEventInitDict = {}),
  Exposed=Window]
 interface FocusEvent : UIEvent {
   readonly attribute EventTarget?   relatedTarget;
diff --git a/components/script/dom/webidls/FormDataEvent.webidl b/components/script/dom/webidls/FormDataEvent.webidl
index d34f57b3a09..e478a33a729 100644
--- a/components/script/dom/webidls/FormDataEvent.webidl
+++ b/components/script/dom/webidls/FormDataEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://html.spec.whatwg.org/multipage/#the-formdataevent-interface
 [Exposed=Window,
- Constructor(DOMString type, optional FormDataEventInit eventInitDict)]
+ Constructor(DOMString type, optional FormDataEventInit eventInitDict = {})]
 interface FormDataEvent : Event {
   readonly attribute FormData formData;
 };
diff --git a/components/script/dom/webidls/GainNode.webidl b/components/script/dom/webidls/GainNode.webidl
index 02bbbacb697..97b205e63e9 100644
--- a/components/script/dom/webidls/GainNode.webidl
+++ b/components/script/dom/webidls/GainNode.webidl
@@ -11,7 +11,7 @@ dictionary GainOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional GainOptions options)]
+ Constructor (BaseAudioContext context, optional GainOptions options = {})]
  interface GainNode : AudioNode {
    readonly attribute AudioParam gain;
  };
diff --git a/components/script/dom/webidls/HashChangeEvent.webidl b/components/script/dom/webidls/HashChangeEvent.webidl
index ec2065aa49e..e5049e75129 100644
--- a/components/script/dom/webidls/HashChangeEvent.webidl
+++ b/components/script/dom/webidls/HashChangeEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#hashchangeevent
-[Constructor(DOMString type, optional HashChangeEventInit eventInitDict),
+[Constructor(DOMString type, optional HashChangeEventInit eventInitDict = {}),
  Exposed=Window]
 interface HashChangeEvent : Event {
   readonly attribute USVString oldURL;
diff --git a/components/script/dom/webidls/InputEvent.webidl b/components/script/dom/webidls/InputEvent.webidl
index 23a62c06b2a..49fb9dc9695 100644
--- a/components/script/dom/webidls/InputEvent.webidl
+++ b/components/script/dom/webidls/InputEvent.webidl
@@ -8,7 +8,7 @@
  */
 
 // https://w3c.github.io/uievents/#idl-inputevent
-[Constructor(DOMString type, optional InputEventInit eventInitDict)]
+[Constructor(DOMString type, optional InputEventInit eventInitDict = {})]
 interface InputEvent : UIEvent {
   readonly attribute DOMString? data;
   readonly attribute boolean isComposing;
diff --git a/components/script/dom/webidls/KeyboardEvent.webidl b/components/script/dom/webidls/KeyboardEvent.webidl
index ed9350a9f29..f30265a87d8 100644
--- a/components/script/dom/webidls/KeyboardEvent.webidl
+++ b/components/script/dom/webidls/KeyboardEvent.webidl
@@ -7,7 +7,7 @@
  *
  */
 
-[Constructor(DOMString typeArg, optional KeyboardEventInit keyboardEventInitDict)]
+[Constructor(DOMString typeArg, optional KeyboardEventInit keyboardEventInitDict = {})]
 interface KeyboardEvent : UIEvent {
     // KeyLocationCode
     const unsigned long DOM_KEY_LOCATION_STANDARD = 0x00;
diff --git a/components/script/dom/webidls/MediaDevices.webidl b/components/script/dom/webidls/MediaDevices.webidl
index 866e1e964d0..0d9c3b9e98b 100644
--- a/components/script/dom/webidls/MediaDevices.webidl
+++ b/components/script/dom/webidls/MediaDevices.webidl
@@ -18,7 +18,7 @@ partial interface Navigator {
 
 partial interface MediaDevices {
     // MediaTrackSupportedConstraints getSupportedConstraints();
-    Promise<MediaStream> getUserMedia(optional MediaStreamConstraints constraints);
+    Promise<MediaStream> getUserMedia(optional MediaStreamConstraints constraints = {});
 };
 
 
diff --git a/components/script/dom/webidls/MediaQueryListEvent.webidl b/components/script/dom/webidls/MediaQueryListEvent.webidl
index 9f194a6feb6..36464230e1b 100644
--- a/components/script/dom/webidls/MediaQueryListEvent.webidl
+++ b/components/script/dom/webidls/MediaQueryListEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://drafts.csswg.org/cssom-view/#dom-mediaquerylistevent-mediaquerylistevent
-[Constructor(DOMString type, optional MediaQueryListEventInit eventInitDict), Exposed=(Window)]
+[Constructor(DOMString type, optional MediaQueryListEventInit eventInitDict = {}), Exposed=(Window)]
 interface MediaQueryListEvent : Event {
   readonly attribute DOMString media;
   readonly attribute boolean matches;
diff --git a/components/script/dom/webidls/MessageEvent.webidl b/components/script/dom/webidls/MessageEvent.webidl
index c2ef9732096..fc43c463743 100644
--- a/components/script/dom/webidls/MessageEvent.webidl
+++ b/components/script/dom/webidls/MessageEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#messageevent
-[Constructor(DOMString type, optional MessageEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional MessageEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface MessageEvent : Event {
   readonly attribute any data;
   readonly attribute DOMString origin;
diff --git a/components/script/dom/webidls/MouseEvent.webidl b/components/script/dom/webidls/MouseEvent.webidl
index 29d5872f65e..ca39c759c04 100644
--- a/components/script/dom/webidls/MouseEvent.webidl
+++ b/components/script/dom/webidls/MouseEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-mouseevent
-[Constructor(DOMString typeArg, optional MouseEventInit mouseEventInitDict),
+[Constructor(DOMString typeArg, optional MouseEventInit mouseEventInitDict = {}),
  Exposed=Window]
 interface MouseEvent : UIEvent {
     readonly    attribute long           screenX;
diff --git a/components/script/dom/webidls/MutationObserver.webidl b/components/script/dom/webidls/MutationObserver.webidl
index 28e59d8244d..a2f223da800 100644
--- a/components/script/dom/webidls/MutationObserver.webidl
+++ b/components/script/dom/webidls/MutationObserver.webidl
@@ -10,7 +10,7 @@
 [Pref="dom.mutation_observer.enabled", Constructor(MutationCallback callback)]
 interface MutationObserver {
     [Throws]
-    void observe(Node target, optional MutationObserverInit options);
+    void observe(Node target, optional MutationObserverInit options = {});
     void disconnect();
     sequence<MutationRecord> takeRecords();
 };
diff --git a/components/script/dom/webidls/Node.webidl b/components/script/dom/webidls/Node.webidl
index 9433e96efa2..37943477bd3 100644
--- a/components/script/dom/webidls/Node.webidl
+++ b/components/script/dom/webidls/Node.webidl
@@ -32,7 +32,7 @@ interface Node : EventTarget {
   readonly attribute Document? ownerDocument;
 
   [Pure]
-  Node getRootNode(optional GetRootNodeOptions options);
+  Node getRootNode(optional GetRootNodeOptions options = {});
 
   [Pure]
   readonly attribute Node? parentNode;
diff --git a/components/script/dom/webidls/OscillatorNode.webidl b/components/script/dom/webidls/OscillatorNode.webidl
index 510b87880a7..ee21e96ffea 100644
--- a/components/script/dom/webidls/OscillatorNode.webidl
+++ b/components/script/dom/webidls/OscillatorNode.webidl
@@ -22,7 +22,7 @@ dictionary OscillatorOptions : AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional OscillatorOptions options)]
+ Constructor (BaseAudioContext context, optional OscillatorOptions options = {})]
 interface OscillatorNode : AudioScheduledSourceNode {
   [SetterThrows]
   attribute OscillatorType type;
diff --git a/components/script/dom/webidls/PageTransitionEvent.webidl b/components/script/dom/webidls/PageTransitionEvent.webidl
index 147a2d2e0c1..c2f438a89b5 100644
--- a/components/script/dom/webidls/PageTransitionEvent.webidl
+++ b/components/script/dom/webidls/PageTransitionEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#the-pagetransitionevent-interface
-[Constructor(DOMString type, optional PageTransitionEventInit eventInitDict),
+[Constructor(DOMString type, optional PageTransitionEventInit eventInitDict = {}),
  Exposed=Window]
 interface PageTransitionEvent : Event {
   readonly attribute boolean persisted;
diff --git a/components/script/dom/webidls/PannerNode.webidl b/components/script/dom/webidls/PannerNode.webidl
index 8c9f8f1913e..08733377fef 100644
--- a/components/script/dom/webidls/PannerNode.webidl
+++ b/components/script/dom/webidls/PannerNode.webidl
@@ -35,7 +35,7 @@ enum PanningModelType {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional PannerOptions options)]
+ Constructor (BaseAudioContext context, optional PannerOptions options = {})]
 interface PannerNode : AudioNode {
   attribute PanningModelType panningModel;
   readonly attribute AudioParam positionX;
diff --git a/components/script/dom/webidls/PopStateEvent.webidl b/components/script/dom/webidls/PopStateEvent.webidl
index 933ec3e7efa..1bd7637a647 100644
--- a/components/script/dom/webidls/PopStateEvent.webidl
+++ b/components/script/dom/webidls/PopStateEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#the-popstateevent-interface
-[Constructor(DOMString type, optional PopStateEventInit eventInitDict),
+[Constructor(DOMString type, optional PopStateEventInit eventInitDict = {}),
  Exposed=Window]
 interface PopStateEvent : Event {
   readonly attribute any state;
diff --git a/components/script/dom/webidls/ProgressEvent.webidl b/components/script/dom/webidls/ProgressEvent.webidl
index 4168c2e6b1d..698ec828877 100644
--- a/components/script/dom/webidls/ProgressEvent.webidl
+++ b/components/script/dom/webidls/ProgressEvent.webidl
@@ -12,7 +12,7 @@
  * http://www.openwebfoundation.org/legal/the-owf-1-0-agreements/owfa-1-0.
  */
 
-[Constructor(DOMString type, optional ProgressEventInit eventInitDict),
+[Constructor(DOMString type, optional ProgressEventInit eventInitDict = {}),
  Exposed=(Window,Worker)]
 interface ProgressEvent : Event {
   readonly attribute boolean lengthComputable;
diff --git a/components/script/dom/webidls/PromiseRejectionEvent.webidl b/components/script/dom/webidls/PromiseRejectionEvent.webidl
index 3a1ee3dc128..43eb391ccfc 100644
--- a/components/script/dom/webidls/PromiseRejectionEvent.webidl
+++ b/components/script/dom/webidls/PromiseRejectionEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://html.spec.whatwg.org/multipage/#the-promiserejectionevent-interface
 
-[Constructor(DOMString type, optional PromiseRejectionEventInit eventInitDict), Exposed=(Window,Worker)]
+[Constructor(DOMString type, optional PromiseRejectionEventInit eventInitDict = {}), Exposed=(Window,Worker)]
 interface PromiseRejectionEvent : Event {
   readonly attribute Promise<any> promise;
   readonly attribute any reason;
diff --git a/components/script/dom/webidls/RTCIceCandidate.webidl b/components/script/dom/webidls/RTCIceCandidate.webidl
index 538805c88db..01fd9a42034 100644
--- a/components/script/dom/webidls/RTCIceCandidate.webidl
+++ b/components/script/dom/webidls/RTCIceCandidate.webidl
@@ -5,7 +5,7 @@
 // https://w3c.github.io/webrtc-pc/#rtcicecandidate-interface
 
 
-[Constructor(optional RTCIceCandidateInit candidateInitDict),
+[Constructor(optional RTCIceCandidateInit candidateInitDict = {}),
  Exposed=Window, Pref="dom.webrtc.enabled"]
 interface RTCIceCandidate {
     readonly attribute DOMString               candidate;
diff --git a/components/script/dom/webidls/RTCPeerConnection.webidl b/components/script/dom/webidls/RTCPeerConnection.webidl
index 58cb7301ea3..b702a70f71d 100644
--- a/components/script/dom/webidls/RTCPeerConnection.webidl
+++ b/components/script/dom/webidls/RTCPeerConnection.webidl
@@ -4,11 +4,11 @@
 
 // https://w3c.github.io/webrtc-pc/#interface-definition
 
-[Constructor(optional RTCConfiguration configuration),
+[Constructor(optional RTCConfiguration configuration = {}),
  Exposed=Window, Pref="dom.webrtc.enabled"]
 interface RTCPeerConnection : EventTarget {
-    Promise<RTCSessionDescriptionInit> createOffer(optional RTCOfferOptions options);
-    Promise<RTCSessionDescriptionInit> createAnswer(optional RTCAnswerOptions options);
+    Promise<RTCSessionDescriptionInit> createOffer(optional RTCOfferOptions options = {});
+    Promise<RTCSessionDescriptionInit> createAnswer(optional RTCAnswerOptions options = {});
     Promise<void>                      setLocalDescription(RTCSessionDescriptionInit description);
     readonly attribute RTCSessionDescription? localDescription;
     // readonly attribute RTCSessionDescription? currentLocalDescription;
@@ -17,7 +17,7 @@ interface RTCPeerConnection : EventTarget {
     readonly attribute RTCSessionDescription? remoteDescription;
     // readonly attribute RTCSessionDescription? currentRemoteDescription;
     // readonly attribute RTCSessionDescription? pendingRemoteDescription;
-    Promise<void>                      addIceCandidate(optional RTCIceCandidateInit candidate);
+    Promise<void>                      addIceCandidate(optional RTCIceCandidateInit candidate = {});
     readonly attribute RTCSignalingState      signalingState;
     readonly attribute RTCIceGatheringState   iceGatheringState;
     readonly attribute RTCIceConnectionState  iceConnectionState;
diff --git a/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl b/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl
index 26a3919b21f..0d2c2b72879 100644
--- a/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl
+++ b/components/script/dom/webidls/RTCPeerConnectionIceEvent.webidl
@@ -4,7 +4,7 @@
 
 // https://w3c.github.io/webrtc-pc/#rtcpeerconnectioniceevent
 
-[Constructor(DOMString type, optional RTCPeerConnectionIceEventInit eventInitDict),
+[Constructor(DOMString type, optional RTCPeerConnectionIceEventInit eventInitDict = {}),
  Exposed=Window, Pref="dom.webrtc.enabled"]
 interface RTCPeerConnectionIceEvent : Event {
     readonly attribute RTCIceCandidate? candidate;
diff --git a/components/script/dom/webidls/Request.webidl b/components/script/dom/webidls/Request.webidl
index 79c1da9bad5..52f258446f3 100644
--- a/components/script/dom/webidls/Request.webidl
+++ b/components/script/dom/webidls/Request.webidl
@@ -6,7 +6,7 @@
 
 typedef (Request or USVString) RequestInfo;
 
-[Constructor(RequestInfo input, optional RequestInit init),
+[Constructor(RequestInfo input, optional RequestInit init = {}),
  Exposed=(Window,Worker)]
 
 interface Request {
diff --git a/components/script/dom/webidls/Response.webidl b/components/script/dom/webidls/Response.webidl
index eaf8fb8b066..7297d64ae9b 100644
--- a/components/script/dom/webidls/Response.webidl
+++ b/components/script/dom/webidls/Response.webidl
@@ -4,7 +4,7 @@
 
 // https://fetch.spec.whatwg.org/#response-class
 
- [Constructor(optional BodyInit? body = null, optional ResponseInit init),
+ [Constructor(optional BodyInit? body = null, optional ResponseInit init = {}),
   Exposed=(Window,Worker)]
 interface Response {
   [NewObject] static Response error();
diff --git a/components/script/dom/webidls/ServiceWorkerContainer.webidl b/components/script/dom/webidls/ServiceWorkerContainer.webidl
index ec7ae1a43e8..18deb5e58f4 100644
--- a/components/script/dom/webidls/ServiceWorkerContainer.webidl
+++ b/components/script/dom/webidls/ServiceWorkerContainer.webidl
@@ -8,7 +8,8 @@ interface ServiceWorkerContainer : EventTarget {
   readonly attribute ServiceWorker? controller;
   //readonly attribute Promise<ServiceWorkerRegistration> ready;
 
-  [NewObject] Promise<ServiceWorkerRegistration> register(USVString scriptURL, optional RegistrationOptions options);
+  [NewObject] Promise<ServiceWorkerRegistration> register(USVString scriptURL,
+                                                          optional RegistrationOptions options = {});
 
   //[NewObject] Promise<any> getRegistration(optional USVString clientURL = "");
   //[NewObject] Promise<FrozenArray<ServiceWorkerRegistration>> getRegistrations();
diff --git a/components/script/dom/webidls/StereoPannerNode.webidl b/components/script/dom/webidls/StereoPannerNode.webidl
index 69b58a408c1..1795ce79bdf 100644
--- a/components/script/dom/webidls/StereoPannerNode.webidl
+++ b/components/script/dom/webidls/StereoPannerNode.webidl
@@ -11,7 +11,7 @@ dictionary StereoPannerOptions: AudioNodeOptions {
 };
 
 [Exposed=Window,
- Constructor (BaseAudioContext context, optional StereoPannerOptions options)]
+ Constructor (BaseAudioContext context, optional StereoPannerOptions options = {})]
 interface StereoPannerNode : AudioScheduledSourceNode {
   readonly attribute AudioParam pan;
 };
diff --git a/components/script/dom/webidls/StorageEvent.webidl b/components/script/dom/webidls/StorageEvent.webidl
index 72330c77f9e..060a82c0d05 100644
--- a/components/script/dom/webidls/StorageEvent.webidl
+++ b/components/script/dom/webidls/StorageEvent.webidl
@@ -9,7 +9,7 @@
  * Event sent to a window when a storage area changes.
  */
 
-[Constructor(DOMString type, optional StorageEventInit eventInitDict), Exposed=Window]
+[Constructor(DOMString type, optional StorageEventInit eventInitDict = {}), Exposed=Window]
 interface StorageEvent : Event {
   readonly attribute DOMString? key;
   readonly attribute DOMString? oldValue;
diff --git a/components/script/dom/webidls/TestBinding.webidl b/components/script/dom/webidls/TestBinding.webidl
index cc942fd06b8..36f91806d4a 100644
--- a/components/script/dom/webidls/TestBinding.webidl
+++ b/components/script/dom/webidls/TestBinding.webidl
@@ -32,7 +32,7 @@ dictionary TestDictionary {
   Blob interfaceValue;
   any anyValue;
   object objectValue;
-  TestDictionaryDefaults dict = null;
+  TestDictionaryDefaults dict = {};
   sequence<TestDictionaryDefaults> seqDict;
   // Testing codegen to import Element correctly, ensure no other code references Element directly
   sequence<Element> elementSequence;
diff --git a/components/script/dom/webidls/TestWorklet.webidl b/components/script/dom/webidls/TestWorklet.webidl
index 3c5d84d2b09..3be494d4825 100644
--- a/components/script/dom/webidls/TestWorklet.webidl
+++ b/components/script/dom/webidls/TestWorklet.webidl
@@ -7,6 +7,6 @@
 
 [Pref="dom.worklet.testing.enabled", Exposed=(Window), Constructor]
 interface TestWorklet {
-   [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options);
+   [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options = {});
    DOMString? lookup(DOMString key);
 };
diff --git a/components/script/dom/webidls/TextDecoder.webidl b/components/script/dom/webidls/TextDecoder.webidl
index 5f1a0cc881a..a2454ab4e05 100644
--- a/components/script/dom/webidls/TextDecoder.webidl
+++ b/components/script/dom/webidls/TextDecoder.webidl
@@ -12,11 +12,11 @@ dictionary TextDecodeOptions {
   boolean stream = false;
 };
 
-[Constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options), Exposed=(Window,Worker)]
+[Constructor(optional DOMString label = "utf-8", optional TextDecoderOptions options = {}), Exposed=(Window,Worker)]
 interface TextDecoder {
   readonly attribute DOMString encoding;
   readonly attribute boolean fatal;
   readonly attribute boolean ignoreBOM;
   [Throws]
-  USVString decode(optional BufferSource input, optional TextDecodeOptions options);
+  USVString decode(optional BufferSource input, optional TextDecodeOptions options = {});
 };
diff --git a/components/script/dom/webidls/TrackEvent.webidl b/components/script/dom/webidls/TrackEvent.webidl
index 214583e3245..f87fa0472a1 100644
--- a/components/script/dom/webidls/TrackEvent.webidl
+++ b/components/script/dom/webidls/TrackEvent.webidl
@@ -5,7 +5,7 @@
 // https://html.spec.whatwg.org/multipage/#the-trackevent-interface
 
 [Exposed=Window,
- Constructor(DOMString type, optional TrackEventInit eventInitDict)]
+ Constructor(DOMString type, optional TrackEventInit eventInitDict = {})]
 interface TrackEvent : Event {
   readonly attribute (VideoTrack or AudioTrack or TextTrack)? track;
 };
diff --git a/components/script/dom/webidls/TransitionEvent.webidl b/components/script/dom/webidls/TransitionEvent.webidl
index 505d6bc2941..05998ececfb 100644
--- a/components/script/dom/webidls/TransitionEvent.webidl
+++ b/components/script/dom/webidls/TransitionEvent.webidl
@@ -6,7 +6,7 @@
  * https://dom.spec.whatwg.org/#event
  */
 
-[Constructor(DOMString type, optional TransitionEventInit transitionEventInitDict),
+[Constructor(DOMString type, optional TransitionEventInit transitionEventInitDict = {}),
  Exposed=Window]
 interface TransitionEvent : Event {
   readonly attribute DOMString          propertyName;
diff --git a/components/script/dom/webidls/UIEvent.webidl b/components/script/dom/webidls/UIEvent.webidl
index 7e895a34448..20be43aec90 100644
--- a/components/script/dom/webidls/UIEvent.webidl
+++ b/components/script/dom/webidls/UIEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-uievent
-[Constructor(DOMString type, optional UIEventInit eventInitDict)]
+[Constructor(DOMString type, optional UIEventInit eventInitDict = {})]
 interface UIEvent : Event {
   //  readonly    attribute WindowProxy? view;
   readonly attribute Window? view;
diff --git a/components/script/dom/webidls/WebGLContextEvent.webidl b/components/script/dom/webidls/WebGLContextEvent.webidl
index 308f3ec7610..f8a2dbf2137 100644
--- a/components/script/dom/webidls/WebGLContextEvent.webidl
+++ b/components/script/dom/webidls/WebGLContextEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15
-[Constructor(DOMString type, optional WebGLContextEventInit eventInit),
+[Constructor(DOMString type, optional WebGLContextEventInit eventInit = {}),
  Exposed=Window]
 interface WebGLContextEvent : Event {
     readonly attribute DOMString statusMessage;
diff --git a/components/script/dom/webidls/WheelEvent.webidl b/components/script/dom/webidls/WheelEvent.webidl
index a38b87dd97d..b202d7f2c24 100644
--- a/components/script/dom/webidls/WheelEvent.webidl
+++ b/components/script/dom/webidls/WheelEvent.webidl
@@ -3,7 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 // https://w3c.github.io/uievents/#interface-wheelevent
-[Constructor(DOMString typeArg, optional WheelEventInit wheelEventInitDict),
+[Constructor(DOMString typeArg, optional WheelEventInit wheelEventInitDict = {}),
  Exposed=Window]
 interface WheelEvent : MouseEvent {
     const unsigned long DOM_DELTA_PIXEL = 0x00;
diff --git a/components/script/dom/webidls/Window.webidl b/components/script/dom/webidls/Window.webidl
index 81ffee9283e..56d9d06a819 100644
--- a/components/script/dom/webidls/Window.webidl
+++ b/components/script/dom/webidls/Window.webidl
@@ -118,11 +118,11 @@ partial interface Window {
   [Replaceable] readonly attribute long pageXOffset;
   [Replaceable] readonly attribute long scrollY;
   [Replaceable] readonly attribute long pageYOffset;
-  void scroll(optional ScrollToOptions options);
+  void scroll(optional ScrollToOptions options = {});
   void scroll(unrestricted double x, unrestricted double y);
-  void scrollTo(optional ScrollToOptions options);
+  void scrollTo(optional ScrollToOptions options = {});
   void scrollTo(unrestricted double x, unrestricted double y);
-  void scrollBy(optional ScrollToOptions options);
+  void scrollBy(optional ScrollToOptions options = {});
   void scrollBy(unrestricted double x, unrestricted double y);
 
   // client
diff --git a/components/script/dom/webidls/Worker.webidl b/components/script/dom/webidls/Worker.webidl
index 2c17e459fa8..f09b565f31a 100644
--- a/components/script/dom/webidls/Worker.webidl
+++ b/components/script/dom/webidls/Worker.webidl
@@ -9,7 +9,7 @@ interface AbstractWorker {
 };
 
 // https://html.spec.whatwg.org/multipage/#worker
-[Constructor(USVString scriptURL, optional WorkerOptions options), Exposed=(Window,Worker)]
+[Constructor(USVString scriptURL, optional WorkerOptions options = {}), Exposed=(Window,Worker)]
 interface Worker : EventTarget {
   void terminate();
 
diff --git a/components/script/dom/webidls/Worklet.webidl b/components/script/dom/webidls/Worklet.webidl
index 9e954925ab0..16ec8e8d7c9 100644
--- a/components/script/dom/webidls/Worklet.webidl
+++ b/components/script/dom/webidls/Worklet.webidl
@@ -5,7 +5,7 @@
 // https://drafts.css-houdini.org/worklets/#worklet
 [Pref="dom.worklet.enabled", Exposed=(Window)]
 interface Worklet {
-    [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options);
+    [NewObject] Promise<void> addModule(USVString moduleURL, optional WorkletOptions options = {});
 };
 
 dictionary WorkletOptions {
diff --git a/components/script/dom/webidls/XR.webidl b/components/script/dom/webidls/XR.webidl
index 58732edd42b..0b3debeaee6 100644
--- a/components/script/dom/webidls/XR.webidl
+++ b/components/script/dom/webidls/XR.webidl
@@ -7,7 +7,7 @@
 interface XR: EventTarget {
   // Methods
   Promise<void> supportsSessionMode(XRSessionMode mode);
-  Promise<XRSession> requestSession(optional XRSessionCreationOptions parameters);
+  Promise<XRSession> requestSession(optional XRSessionCreationOptions parameters = {});
 
   // Events
   // attribute EventHandler ondevicechange;
diff --git a/components/script/dom/webidls/XRRigidTransform.webidl b/components/script/dom/webidls/XRRigidTransform.webidl
index 089dc1732a6..b58a8c339e4 100644
--- a/components/script/dom/webidls/XRRigidTransform.webidl
+++ b/components/script/dom/webidls/XRRigidTransform.webidl
@@ -5,7 +5,7 @@
 // https://immersive-web.github.io/webxr/#xrrigidtransform-interface
 
 [SecureContext, Exposed=Window, Pref="dom.webxr.enabled",
- Constructor(optional DOMPointInit position, optional DOMPointInit orientation)]
+ Constructor(optional DOMPointInit position = {}, optional DOMPointInit orientation = {})]
 interface XRRigidTransform {
   readonly attribute DOMPointReadOnly position;
   readonly attribute DOMPointReadOnly orientation;
diff --git a/components/script/dom/webidls/XRSession.webidl b/components/script/dom/webidls/XRSession.webidl
index 59ccecb521a..d35f724f87e 100644
--- a/components/script/dom/webidls/XRSession.webidl
+++ b/components/script/dom/webidls/XRSession.webidl
@@ -29,7 +29,7 @@ interface XRSession : EventTarget {
   // FrozenArray<XRInputSource> getInputSources();
   sequence<XRInputSource> getInputSources();
 
-  void updateRenderState(optional XRRenderStateInit state);
+  void updateRenderState(optional XRRenderStateInit state = {});
   long requestAnimationFrame(XRFrameRequestCallback callback);
   void cancelAnimationFrame(long handle);
 
diff --git a/components/script/dom/webidls/XRWebGLLayer.webidl b/components/script/dom/webidls/XRWebGLLayer.webidl
index 0df8296be34..f551096fc05 100644
--- a/components/script/dom/webidls/XRWebGLLayer.webidl
+++ b/components/script/dom/webidls/XRWebGLLayer.webidl
@@ -19,7 +19,7 @@ dictionary XRWebGLLayerInit {
 
 [SecureContext, Exposed=Window, Constructor(XRSession session,
             XRWebGLRenderingContext context,
-            optional XRWebGLLayerInit layerInit),
+            optional XRWebGLLayerInit layerInit = {}),
     Pref="dom.webxr.enabled"]
 interface XRWebGLLayer : XRLayer {
   // // Attributes