Auto merge of #25272 - pshaughn:domexception_inherits_tostring, r=Manishearth

DOMException now inherits its Javascript toString from Error

<!-- Please describe your changes on the following line: -->
stringifier is out of the DOMException IDL, and Stringifier(&self) is moved into the main body of DOMException where it can continue to be called internally.

---
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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 #25042

<!-- Either: -->
- [X] There are tests for these changes

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components/script/dom/bindings/error.rs

@@ -6,7 +6,6 @@
 
 #[cfg(feature = "js_backtrace")]
 use crate::dom::bindings::cell::DomRefCell;
-use crate::dom::bindings::codegen::Bindings::DOMExceptionBinding::DOMExceptionMethods;
 use crate::dom::bindings::codegen::PrototypeList::proto_id_to_name;
 use crate::dom::bindings::conversions::root_from_object;
 use crate::dom::bindings::conversions::{
@@ -221,7 +220,7 @@ impl ErrorInfo {
 
         Some(ErrorInfo {
             filename: "".to_string(),
-            message: exception.Stringifier().into(),
+            message: exception.stringifier().into(),
             lineno: 0,
             column: 0,
         })

components/script/dom/domexception.rs

@@ -149,6 +149,11 @@ impl DOMException {
             DOMExceptionBinding::Wrap,
         ))
     }
+
+    // not an IDL stringifier, used internally
+    pub fn stringifier(&self) -> DOMString {
+        DOMString::from(format!("{}: {}", self.name, self.message))
+    }
 }
 
 impl DOMExceptionMethods for DOMException {
@@ -169,9 +174,4 @@ impl DOMExceptionMethods for DOMException {
     fn Message(&self) -> DOMString {
         self.message.clone()
     }
-
-    // https://people.mozilla.org/~jorendorff/es6-draft.html#sec-error.prototype.tostring
-    fn Stringifier(&self) -> DOMString {
-        DOMString::from(format!("{}: {}", self.name, self.message))
-    }
 }

components/script/dom/webidls/DOMException.webidl

@@ -47,6 +47,4 @@ interface DOMException {
 
   // A custom message set by the thrower.
   readonly attribute DOMString message;
-
-  stringifier;
 };

tests/wpt/metadata/WebIDL/ecmascript-binding/es-exceptions/DOMException-custom-bindings.any.js.ini

@@ -1,17 +0,0 @@
-[DOMException-custom-bindings.any.worker.html]
-  type: testharness
-  [Inherits its toString() from Error.prototype]
-    expected: FAIL
-
-  [toString() behavior from Error.prototype applies as expected]
-    expected: FAIL
-
-
-[DOMException-custom-bindings.any.html]
-  type: testharness
-  [Inherits its toString() from Error.prototype]
-    expected: FAIL
-
-  [toString() behavior from Error.prototype applies as expected]
-    expected: FAIL
-