Auto merge of #25367 - pshaughn:ce_undefined_is, r=jdm

apply is: to Document.createElement even when name isn't registered yet

The "is" option to Document.createElement should be respected even when the name hasn't been registered yet, in which case the name gets looked up again at the time the element should be upgraded. This change does that.
I'm now seeing a few test timeouts that aren't in the metadata, but I suspect they're slowness on my local configuration and not actual breakage.

---
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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 #25009 fix #24997 and fix #24998

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- [X] There are tests for these changes OR

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2 files changed, 37 insertions, 19 deletions

diff --git a/components/script/dom/create.rs b/components/script/dom/create.rs
index e992a8707dd..c45e4286992 100644
--- a/components/script/dom/create.rs
+++ b/components/script/dom/create.rs
@@ -189,14 +189,21 @@ fn create_html_element(
         }
     }
 
-    // Steps 7.1-7.2
+    // Steps 7.1-7.3
     let result = create_native_html_element(name.clone(), prefix, document, creator);
+    match is {
+        Some(is) => {
+            result.set_is(is);
+            result.set_custom_element_state(CustomElementState::Undefined);
+        },
+        None => {
+            if is_valid_custom_element_name(&*name.local) {
+                result.set_custom_element_state(CustomElementState::Undefined);
+            }
+        },
+    };
 
-    // Step 7.3
-    if is_valid_custom_element_name(&*name.local) || is.is_some() {
-        result.set_custom_element_state(CustomElementState::Undefined);
-    }
-
+    // Step 8
     result
 }
 
diff --git a/components/script/dom/customelementregistry.rs b/components/script/dom/customelementregistry.rs
index 7b4229835e2..dbeacdc7ebb 100644
--- a/components/script/dom/customelementregistry.rs
+++ b/components/script/dom/customelementregistry.rs
@@ -581,7 +581,9 @@ pub fn upgrade_element(definition: Rc<CustomElementDefinition>, element: &Elemen
         return;
     }
 
-    // Step 3
+    // Step 3 happens later to save having to undo it in an exception
+
+    // Step 4
     for attr in element.attrs().iter() {
         let local_name = attr.local_name().clone();
         let value = DOMString::from(&**attr.value());
@@ -593,7 +595,7 @@ pub fn upgrade_element(definition: Rc<CustomElementDefinition>, element: &Elemen
         );
     }
 
-    // Step 4
+    // Step 5
     if element.is_connected() {
         ScriptThread::enqueue_callback_reaction(
             element,
@@ -602,44 +604,51 @@ pub fn upgrade_element(definition: Rc<CustomElementDefinition>, element: &Elemen
         );
     }
 
-    // Step 5
+    // Step 6
     definition
         .construction_stack
         .borrow_mut()
         .push(ConstructionStackEntry::Element(DomRoot::from_ref(element)));
 
-    // Step 7
+    // Steps 7-8, successful case
     let result = run_upgrade_constructor(&definition.constructor, element);
 
+    // "regardless of whether the above steps threw an exception" step
     definition.construction_stack.borrow_mut().pop();
 
-    // Step 7 exception handling
+    // Step 8 exception handling
     if let Err(error) = result {
-        // Step 7.1
+        // Step 8.exception.1
         element.set_custom_element_state(CustomElementState::Failed);
 
-        // Step 7.2
+        // Step 8.exception.2 isn't needed since step 3 hasn't happened yet
+
+        // Step 8.exception.3
         element.clear_reaction_queue();
 
-        // Step 7.3
+        // Step 8.exception.4
         let global = GlobalScope::current().expect("No current global");
         let cx = global.get_cx();
         unsafe {
             throw_dom_exception(cx, &global, error);
             report_pending_exception(*cx, true);
         }
+
         return;
     }
 
-    // Step 8
+    // TODO Step 9: "If element is a form-associated custom element..."
+
+    // Step 10
+
     element.set_custom_element_state(CustomElementState::Custom);
 
-    // Step 9
+    // Step 3
     element.set_custom_element_definition(definition);
 }
 
 /// <https://html.spec.whatwg.org/multipage/#concept-upgrade-an-element>
-/// Steps 7.1-7.2
+/// Steps 8.1-8.3
 #[allow(unsafe_code)]
 fn run_upgrade_constructor(
     constructor: &Rc<CustomElementConstructor>,
@@ -654,10 +663,12 @@ fn run_upgrade_constructor(
     }
     rooted!(in(*cx) let mut construct_result = ptr::null_mut::<JSObject>());
     {
+        // Step 8.1 TODO when shadow DOM exists
+
         // Go into the constructor's compartment
         let _ac = JSAutoRealm::new(*cx, constructor.callback());
         let args = HandleValueArray::new();
-        // Step 7.1
+        // Step 8.2
         if unsafe {
             !Construct1(
                 *cx,
@@ -668,7 +679,7 @@ fn run_upgrade_constructor(
         } {
             return Err(Error::JSFailed);
         }
-        // Step 7.2
+        // Step 8.3
         let mut same = false;
         rooted!(in(*cx) let construct_result_val = ObjectValue(construct_result.get()));
         if unsafe {