Auto merge of #23844 - saschanaz:tojson, r=Manishearth

Support default toJSON in WebIDL

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Ported related lines from gecko.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #22781

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- [x] There are tests for these changes

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components/script/dom/webidls/DOMMatrixReadOnly.webidl

@@ -81,7 +81,6 @@ interface DOMMatrixReadOnly {
     DOMPoint            transformPoint(optional DOMPointInit point = {});
     Float32Array        toFloat32Array();
     Float64Array        toFloat64Array();
-//                      stringifier;
-//                      serializer = { attribute };
-
+//    [Exposed=Window] stringifier;
+    [Default] object toJSON();
 };

components/script/dom/webidls/DOMPointReadOnly.webidl

@@ -20,4 +20,6 @@ interface DOMPointReadOnly {
     readonly attribute unrestricted double y;
     readonly attribute unrestricted double z;
     readonly attribute unrestricted double w;
+
+    [Default] object toJSON();
 };

components/script/dom/webidls/DOMQuad.webidl

@@ -22,6 +22,8 @@ interface DOMQuad {
     [SameObject] readonly attribute DOMPoint p3;
     [SameObject] readonly attribute DOMPoint p4;
     [NewObject] DOMRect getBounds();
+
+    [Default] object toJSON();
 };
 
 dictionary DOMQuadInit {

components/script/dom/webidls/DOMRectReadOnly.webidl

@@ -17,6 +17,8 @@ interface DOMRectReadOnly {
   readonly attribute unrestricted double right;
   readonly attribute unrestricted double bottom;
   readonly attribute unrestricted double left;
+
+  [Default] object toJSON();
 };
 
 // https://drafts.fxtf.org/geometry/#dictdef-domrectinit