Auto merge of #17224 - cbrewster:html_constructor, r=jdm

WebIDL HTMLConstructor support

<!-- Please describe your changes on the following line: -->
spec: https://html.spec.whatwg.org/multipage/#htmlconstructor

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #17194 (github issue number if applicable).

<!-- Either: -->
- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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Cargo.lock

@@ -1372,7 +1372,7 @@ dependencies = [
 [[package]]
 name = "js"
 version = "0.1.6"
-source = "git+https://github.com/servo/rust-mozjs#bc7af508c194d56eef3a2c52772ae261b9a1facb"
+source = "git+https://github.com/servo/rust-mozjs#3de4ff3d52361a47a17e3b4fcb02c779b99d93d4"
 dependencies = [
  "cmake 0.1.22 (registry+https://github.com/rust-lang/crates.io-index)",
  "heapsize 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",

components/script/dom/bindings/codegen/CodegenRust.py

@@ -2863,7 +2863,7 @@ create_noncallback_interface_object(cx,
                                     %(length)s,
                                     interface.handle_mut());
 assert!(!interface.is_null());""" % properties))
-            if self.descriptor.hasDescendants():
+            if self.descriptor.shouldCacheConstructor():
                 code.append(CGGeneric("""\
 assert!((*cache)[PrototypeList::Constructor::%(id)s as usize].is_null());
 (*cache)[PrototypeList::Constructor::%(id)s as usize] = interface.get();
@@ -5301,11 +5301,79 @@ class CGClassConstructHook(CGAbstractExternMethod):
             preamble += "let global = Root::downcast::<dom::types::%s>(global).unwrap();\n" % list(self.exposureSet)[0]
         preamble += """let args = CallArgs::from_vp(vp, argc);\n"""
         preamble = CGGeneric(preamble)
+        if self.constructor.isHTMLConstructor():
+            signatures = self.constructor.signatures()
+            assert len(signatures) == 1
+            constructorCall = CGGeneric("""\
+// Step 2 https://html.spec.whatwg.org/multipage/#htmlconstructor
+// The custom element definition cannot use an element interface as its constructor
+
+// The new_target might be a cross-compartment wrapper. Get the underlying object
+// so we can do the spec's object-identity checks.
+rooted!(in(cx) let new_target = UnwrapObject(args.new_target().to_object(), 1));
+if new_target.is_null() {
+    throw_dom_exception(cx, global.upcast::<GlobalScope>(), Error::Type("new.target is null".to_owned()));
+    return false;
+}
+
+if args.callee() == new_target.get() {
+    throw_dom_exception(cx, global.upcast::<GlobalScope>(),
+        Error::Type("new.target must not be the active function object".to_owned()));
+    return false;
+}
+
+// Step 6
+rooted!(in(cx) let mut prototype = ptr::null_mut());
+{
+    rooted!(in(cx) let mut proto_val = UndefinedValue());
+    let _ac = JSAutoCompartment::new(cx, new_target.get());
+    if !JS_GetProperty(cx, new_target.handle(), b"prototype\\0".as_ptr() as *const _, proto_val.handle_mut()) {
+        return false;
+    }
+
+    if !proto_val.is_object() {
+        // Step 7 of https://html.spec.whatwg.org/multipage/#htmlconstructor.
+        // This fallback behavior is designed to match analogous behavior for the
+        // JavaScript built-ins. So we enter the compartment of our underlying
+        // newTarget object and fall back to the prototype object from that global.
+        // XXX The spec says to use GetFunctionRealm(), which is not actually
+        // the same thing as what we have here (e.g. in the case of scripted callable proxies
+        // whose target is not same-compartment with the proxy, or bound functions, etc).
+        // https://bugzilla.mozilla.org/show_bug.cgi?id=1317658
+
+        rooted!(in(cx) let global_object = CurrentGlobalOrNull(cx));
+        GetProtoObject(cx, global_object.handle(), prototype.handle_mut());
+    } else {
+        // Step 6
+        prototype.set(proto_val.to_object());
+    };
+}
+
+// Wrap prototype in this context since it is from the newTarget compartment
+if !JS_WrapObject(cx, prototype.handle_mut()) {
+    return false;
+}
+
+let result: Result<Root<%s>, Error> = html_constructor(&global, &args);
+let result = match result {
+    Ok(result) => result,
+    Err(e) => {
+        throw_dom_exception(cx, global.upcast::<GlobalScope>(), e);
+        return false;
+    },
+};
+
+JS_SetPrototype(cx, result.reflector().get_jsobject(), prototype.handle());
+
+(result).to_jsval(cx, args.rval());
+return true;
+""" % self.descriptor.name)
+        else:
             name = self.constructor.identifier.name
             nativeName = MakeNativeName(self.descriptor.binaryNameFor(name))
-        callGenerator = CGMethodCall(["&global"], nativeName, True,
+            constructorCall = CGMethodCall(["&global"], nativeName, True,
                                            self.descriptor, self.constructor)
-        return CGList([preamble, callGenerator])
+        return CGList([preamble, constructorCall])
 
 
 class CGClassFinalizeHook(CGAbstractClassHook):
@@ -5517,9 +5585,11 @@ def generate_imports(config, cgthings, descriptors, callbacks=None, dictionaries
         'js::jsapi::JS_ObjectIsDate',
         'js::jsapi::JS_SetImmutablePrototype',
         'js::jsapi::JS_SetProperty',
+        'js::jsapi::JS_SetPrototype',
         'js::jsapi::JS_SetReservedSlot',
         'js::jsapi::JS_SplicePrototype',
         'js::jsapi::JS_WrapValue',
+        'js::jsapi::JS_WrapObject',
         'js::jsapi::MutableHandle',
         'js::jsapi::MutableHandleObject',
         'js::jsapi::MutableHandleValue',
@@ -5547,6 +5617,7 @@ def generate_imports(config, cgthings, descriptors, callbacks=None, dictionaries
         'js::glue::RUST_JSID_IS_STRING',
         'js::glue::RUST_SYMBOL_TO_JSID',
         'js::glue::int_to_jsid',
+        'js::glue::UnwrapObject',
         'js::panic::maybe_resume_unwind',
         'js::panic::wrap_panic',
         'js::rust::GCMethods',
@@ -5561,14 +5632,15 @@ def generate_imports(config, cgthings, descriptors, callbacks=None, dictionaries
         'dom::bindings::interface::ConstructorClassHook',
         'dom::bindings::interface::InterfaceConstructorBehavior',
         'dom::bindings::interface::NonCallbackInterfaceObjectClass',
-        'dom::bindings::interface::create_callback_interface_object',
         'dom::bindings::interface::create_global_object',
+        'dom::bindings::interface::create_callback_interface_object',
         'dom::bindings::interface::create_interface_prototype_object',
         'dom::bindings::interface::create_named_constructors',
         'dom::bindings::interface::create_noncallback_interface_object',
         'dom::bindings::interface::define_guarded_constants',
         'dom::bindings::interface::define_guarded_methods',
         'dom::bindings::interface::define_guarded_properties',
+        'dom::bindings::interface::html_constructor',
         'dom::bindings::interface::is_exposed_in',
         'dom::bindings::iterable::Iterable',
         'dom::bindings::iterable::IteratorType',

components/script/dom/bindings/codegen/Configuration.py

@@ -398,7 +398,11 @@ class Descriptor(DescriptorProvider):
         assert self.interface.hasInterfaceObject()
         if self.interface.getExtendedAttribute("Inline"):
             return False
-        return self.interface.isCallback() or self.interface.isNamespace() or self.hasDescendants()
+        return (self.interface.isCallback() or self.interface.isNamespace() or
+                self.hasDescendants() or self.interface.getExtendedAttribute("HTMLConstructor"))
+
+    def shouldCacheConstructor(self):
+        return self.hasDescendants() or self.interface.getExtendedAttribute("HTMLConstructor")
 
     def isExposedConditionally(self):
         return self.interface.isExposedConditionally()

components/script/dom/bindings/interface.rs

@@ -4,17 +4,92 @@
 
 //! Machinery to initialise interface prototype objects and interface objects.
 
+use dom::bindings::codegen::Bindings::HTMLAnchorElementBinding;
+use dom::bindings::codegen::Bindings::HTMLAreaElementBinding;
+use dom::bindings::codegen::Bindings::HTMLAudioElementBinding;
+use dom::bindings::codegen::Bindings::HTMLBRElementBinding;
+use dom::bindings::codegen::Bindings::HTMLBaseElementBinding;
+use dom::bindings::codegen::Bindings::HTMLBodyElementBinding;
+use dom::bindings::codegen::Bindings::HTMLButtonElementBinding;
+use dom::bindings::codegen::Bindings::HTMLCanvasElementBinding;
+use dom::bindings::codegen::Bindings::HTMLDListElementBinding;
+use dom::bindings::codegen::Bindings::HTMLDataElementBinding;
+use dom::bindings::codegen::Bindings::HTMLDataListElementBinding;
+use dom::bindings::codegen::Bindings::HTMLDetailsElementBinding;
+use dom::bindings::codegen::Bindings::HTMLDialogElementBinding;
+use dom::bindings::codegen::Bindings::HTMLDirectoryElementBinding;
+use dom::bindings::codegen::Bindings::HTMLDivElementBinding;
+use dom::bindings::codegen::Bindings::HTMLElementBinding;
+use dom::bindings::codegen::Bindings::HTMLEmbedElementBinding;
+use dom::bindings::codegen::Bindings::HTMLFieldSetElementBinding;
+use dom::bindings::codegen::Bindings::HTMLFontElementBinding;
+use dom::bindings::codegen::Bindings::HTMLFormElementBinding;
+use dom::bindings::codegen::Bindings::HTMLFrameElementBinding;
+use dom::bindings::codegen::Bindings::HTMLFrameSetElementBinding;
+use dom::bindings::codegen::Bindings::HTMLHRElementBinding;
+use dom::bindings::codegen::Bindings::HTMLHeadElementBinding;
+use dom::bindings::codegen::Bindings::HTMLHeadingElementBinding;
+use dom::bindings::codegen::Bindings::HTMLHtmlElementBinding;
+use dom::bindings::codegen::Bindings::HTMLIFrameElementBinding;
+use dom::bindings::codegen::Bindings::HTMLImageElementBinding;
+use dom::bindings::codegen::Bindings::HTMLInputElementBinding;
+use dom::bindings::codegen::Bindings::HTMLLIElementBinding;
+use dom::bindings::codegen::Bindings::HTMLLabelElementBinding;
+use dom::bindings::codegen::Bindings::HTMLLegendElementBinding;
+use dom::bindings::codegen::Bindings::HTMLLinkElementBinding;
+use dom::bindings::codegen::Bindings::HTMLMapElementBinding;
+use dom::bindings::codegen::Bindings::HTMLMetaElementBinding;
+use dom::bindings::codegen::Bindings::HTMLMeterElementBinding;
+use dom::bindings::codegen::Bindings::HTMLModElementBinding;
+use dom::bindings::codegen::Bindings::HTMLOListElementBinding;
+use dom::bindings::codegen::Bindings::HTMLObjectElementBinding;
+use dom::bindings::codegen::Bindings::HTMLOptGroupElementBinding;
+use dom::bindings::codegen::Bindings::HTMLOptionElementBinding;
+use dom::bindings::codegen::Bindings::HTMLOutputElementBinding;
+use dom::bindings::codegen::Bindings::HTMLParagraphElementBinding;
+use dom::bindings::codegen::Bindings::HTMLParamElementBinding;
+use dom::bindings::codegen::Bindings::HTMLPreElementBinding;
+use dom::bindings::codegen::Bindings::HTMLProgressElementBinding;
+use dom::bindings::codegen::Bindings::HTMLQuoteElementBinding;
+use dom::bindings::codegen::Bindings::HTMLScriptElementBinding;
+use dom::bindings::codegen::Bindings::HTMLSelectElementBinding;
+use dom::bindings::codegen::Bindings::HTMLSourceElementBinding;
+use dom::bindings::codegen::Bindings::HTMLSpanElementBinding;
+use dom::bindings::codegen::Bindings::HTMLStyleElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTableCaptionElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTableColElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTableDataCellElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTableElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTableHeaderCellElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTableRowElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTableSectionElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTemplateElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTextAreaElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTimeElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTitleElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTrackElementBinding;
+use dom::bindings::codegen::Bindings::HTMLUListElementBinding;
+use dom::bindings::codegen::Bindings::HTMLVideoElementBinding;
+use dom::bindings::codegen::Bindings::WindowBinding::WindowMethods;
 use dom::bindings::codegen::InterfaceObjectMap::Globals;
 use dom::bindings::codegen::PrototypeList;
 use dom::bindings::constant::{ConstantSpec, define_constants};
-use dom::bindings::conversions::{DOM_OBJECT_SLOT, get_dom_class};
+use dom::bindings::conversions::{DOM_OBJECT_SLOT, DerivedFrom, get_dom_class};
+use dom::bindings::error::{Error, Fallible};
 use dom::bindings::guard::Guard;
+use dom::bindings::js::Root;
 use dom::bindings::utils::{DOM_PROTOTYPE_SLOT, ProtoOrIfaceArray, get_proto_or_iface_array};
+use dom::create::create_native_html_element;
+use dom::element::{Element, ElementCreator};
+use dom::htmlelement::HTMLElement;
+use dom::window::Window;
+use html5ever::LocalName;
+use html5ever::interface::QualName;
 use js::error::throw_type_error;
-use js::glue::{RUST_SYMBOL_TO_JSID, UncheckedUnwrapObject};
+use js::glue::{RUST_SYMBOL_TO_JSID, UncheckedUnwrapObject, UnwrapObject};
-use js::jsapi::{Class, ClassOps, CompartmentOptions, GetGlobalForObjectCrossCompartment};
+use js::jsapi::{CallArgs, Class, ClassOps, CompartmentOptions, CurrentGlobalOrNull};
-use js::jsapi::{GetWellKnownSymbol, HandleObject, HandleValue, JSAutoCompartment};
+use js::jsapi::{GetGlobalForObjectCrossCompartment, GetWellKnownSymbol, HandleObject, HandleValue};
-use js::jsapi::{JSClass, JSContext, JSFUN_CONSTRUCTOR, JSFunctionSpec, JSObject};
+use js::jsapi::{JSAutoCompartment, JSClass, JSContext, JSFUN_CONSTRUCTOR, JSFunctionSpec, JSObject};
 use js::jsapi::{JSPROP_PERMANENT, JSPROP_READONLY, JSPROP_RESOLVING};
 use js::jsapi::{JSPropertySpec, JSString, JSTracer, JSVersion, JS_AtomizeAndPinString};
 use js::jsapi::{JS_DefineProperty, JS_DefineProperty1, JS_DefineProperty2};
@@ -158,6 +233,73 @@ pub unsafe fn create_global_object(
     JS_FireOnNewGlobalObject(cx, rval.handle());
 }
 
+// https://html.spec.whatwg.org/multipage/#htmlconstructor
+pub unsafe fn html_constructor<T>(window: &Window, call_args: &CallArgs) -> Fallible<Root<T>>
+                                  where T: DerivedFrom<Element> {
+    let document = window.Document();
+
+    // Step 1
+    let registry = window.CustomElements();
+
+    // Step 2 is checked in the generated caller code
+
+    // Step 3
+    rooted!(in(window.get_cx()) let new_target = call_args.new_target().to_object());
+    let definition = match registry.lookup_definition_by_constructor(new_target.handle()) {
+        Some(definition) => definition,
+        None => return Err(Error::Type("No custom element definition found for new.target".to_owned())),
+    };
+
+    rooted!(in(window.get_cx()) let callee = UnwrapObject(call_args.callee(), 1));
+    if callee.is_null() {
+        return Err(Error::Security);
+    }
+
+    {
+        let _ac = JSAutoCompartment::new(window.get_cx(), callee.get());
+        rooted!(in(window.get_cx()) let mut constructor = ptr::null_mut());
+        rooted!(in(window.get_cx()) let global_object = CurrentGlobalOrNull(window.get_cx()));
+
+        if definition.is_autonomous() {
+            // Step 4
+            // Since this element is autonomous, its active function object must be the HTMLElement
+
+            // Retrieve the constructor object for HTMLElement
+            HTMLElementBinding::GetConstructorObject(window.get_cx(), global_object.handle(), constructor.handle_mut());
+
+        } else {
+            // Step 5
+            get_constructor_object_from_local_name(definition.local_name.clone(),
+                                                   window.get_cx(),
+                                                   global_object.handle(),
+                                                   constructor.handle_mut());
+        }
+        // Callee must be the same as the element interface's constructor object.
+        if constructor.get() != callee.get() {
+            return Err(Error::Type("Custom element does not extend the proper interface".to_owned()));
+        }
+    }
+
+    // Step 8.1
+    let name = QualName::new(None, ns!(html), definition.local_name.clone());
+    let element = if definition.is_autonomous() {
+        Root::upcast(HTMLElement::new(name.local, None, &*document))
+    } else {
+        create_native_html_element(name, None, &*document, ElementCreator::ScriptCreated)
+    };
+
+    // Step 8.2 is performed in the generated caller code.
+
+    // TODO: Step 8.3 - 8.4
+    // Set the element's custom element state and definition.
+
+    // Step 8.5
+    Root::downcast(element).ok_or(Error::InvalidState)
+
+    // TODO: Steps 9-13
+    // Custom element upgrades are not implemented yet, so these steps are unnecessary.
+}
+
 /// Create and define the interface object of a callback interface.
 pub unsafe fn create_callback_interface_object(
         cx: *mut JSContext,
@@ -474,3 +616,146 @@ unsafe extern "C" fn non_new_constructor(
     throw_type_error(cx, "This constructor needs to be called with `new`.");
     false
 }
+
+/// Returns the constructor object for the element associated with the given local name.
+/// This list should only include elements marked with the [HTMLConstructor] extended attribute.
+pub fn get_constructor_object_from_local_name(name: LocalName,
+                                              cx: *mut JSContext,
+                                              global: HandleObject,
+                                              rval: MutableHandleObject)
+                                              -> bool {
+    macro_rules! get_constructor(
+        ($binding:ident) => ({
+            unsafe { $binding::GetConstructorObject(cx, global, rval); }
+            true
+        })
+    );
+
+    match name {
+        local_name!("a")          => get_constructor!(HTMLAnchorElementBinding),
+        local_name!("abbr")       => get_constructor!(HTMLElementBinding),
+        local_name!("acronym")    => get_constructor!(HTMLElementBinding),
+        local_name!("address")    => get_constructor!(HTMLElementBinding),
+        local_name!("area")       => get_constructor!(HTMLAreaElementBinding),
+        local_name!("article")    => get_constructor!(HTMLElementBinding),
+        local_name!("aside")      => get_constructor!(HTMLElementBinding),
+        local_name!("audio")      => get_constructor!(HTMLAudioElementBinding),
+        local_name!("b")          => get_constructor!(HTMLElementBinding),
+        local_name!("base")       => get_constructor!(HTMLBaseElementBinding),
+        local_name!("bdi")        => get_constructor!(HTMLElementBinding),
+        local_name!("bdo")        => get_constructor!(HTMLElementBinding),
+        local_name!("big")        => get_constructor!(HTMLElementBinding),
+        local_name!("blockquote") => get_constructor!(HTMLQuoteElementBinding),
+        local_name!("body")       => get_constructor!(HTMLBodyElementBinding),
+        local_name!("br")         => get_constructor!(HTMLBRElementBinding),
+        local_name!("button")     => get_constructor!(HTMLButtonElementBinding),
+        local_name!("canvas")     => get_constructor!(HTMLCanvasElementBinding),
+        local_name!("caption")    => get_constructor!(HTMLTableCaptionElementBinding),
+        local_name!("center")     => get_constructor!(HTMLElementBinding),
+        local_name!("cite")       => get_constructor!(HTMLElementBinding),
+        local_name!("code")       => get_constructor!(HTMLElementBinding),
+        local_name!("col")        => get_constructor!(HTMLTableColElementBinding),
+        local_name!("colgroup")   => get_constructor!(HTMLTableColElementBinding),
+        local_name!("data")       => get_constructor!(HTMLDataElementBinding),
+        local_name!("datalist")   => get_constructor!(HTMLDataListElementBinding),
+        local_name!("dd")         => get_constructor!(HTMLElementBinding),
+        local_name!("del")        => get_constructor!(HTMLModElementBinding),
+        local_name!("details")    => get_constructor!(HTMLDetailsElementBinding),
+        local_name!("dfn")        => get_constructor!(HTMLElementBinding),
+        local_name!("dialog")     => get_constructor!(HTMLDialogElementBinding),
+        local_name!("dir")        => get_constructor!(HTMLDirectoryElementBinding),
+        local_name!("div")        => get_constructor!(HTMLDivElementBinding),
+        local_name!("dl")         => get_constructor!(HTMLDListElementBinding),
+        local_name!("dt")         => get_constructor!(HTMLElementBinding),
+        local_name!("em")         => get_constructor!(HTMLElementBinding),
+        local_name!("embed")      => get_constructor!(HTMLEmbedElementBinding),
+        local_name!("fieldset")   => get_constructor!(HTMLFieldSetElementBinding),
+        local_name!("figcaption") => get_constructor!(HTMLElementBinding),
+        local_name!("figure")     => get_constructor!(HTMLElementBinding),
+        local_name!("font")       => get_constructor!(HTMLFontElementBinding),
+        local_name!("footer")     => get_constructor!(HTMLElementBinding),
+        local_name!("form")       => get_constructor!(HTMLFormElementBinding),
+        local_name!("frame")      => get_constructor!(HTMLFrameElementBinding),
+        local_name!("frameset")   => get_constructor!(HTMLFrameSetElementBinding),
+        local_name!("h1")         => get_constructor!(HTMLHeadingElementBinding),
+        local_name!("h2")         => get_constructor!(HTMLHeadingElementBinding),
+        local_name!("h3")         => get_constructor!(HTMLHeadingElementBinding),
+        local_name!("h4")         => get_constructor!(HTMLHeadingElementBinding),
+        local_name!("h5")         => get_constructor!(HTMLHeadingElementBinding),
+        local_name!("h6")         => get_constructor!(HTMLHeadingElementBinding),
+        local_name!("head")       => get_constructor!(HTMLHeadElementBinding),
+        local_name!("header")     => get_constructor!(HTMLElementBinding),
+        local_name!("hgroup")     => get_constructor!(HTMLElementBinding),
+        local_name!("hr")         => get_constructor!(HTMLHRElementBinding),
+        local_name!("html")       => get_constructor!(HTMLHtmlElementBinding),
+        local_name!("i")          => get_constructor!(HTMLElementBinding),
+        local_name!("iframe")     => get_constructor!(HTMLIFrameElementBinding),
+        local_name!("img")        => get_constructor!(HTMLImageElementBinding),
+        local_name!("input")      => get_constructor!(HTMLInputElementBinding),
+        local_name!("ins")        => get_constructor!(HTMLModElementBinding),
+        local_name!("kbd")        => get_constructor!(HTMLElementBinding),
+        local_name!("label")      => get_constructor!(HTMLLabelElementBinding),
+        local_name!("legend")     => get_constructor!(HTMLLegendElementBinding),
+        local_name!("li")         => get_constructor!(HTMLLIElementBinding),
+        local_name!("link")       => get_constructor!(HTMLLinkElementBinding),
+        local_name!("listing")    => get_constructor!(HTMLPreElementBinding),
+        local_name!("main")       => get_constructor!(HTMLElementBinding),
+        local_name!("map")        => get_constructor!(HTMLMapElementBinding),
+        local_name!("mark")       => get_constructor!(HTMLElementBinding),
+        local_name!("marquee")    => get_constructor!(HTMLElementBinding),
+        local_name!("meta")       => get_constructor!(HTMLMetaElementBinding),
+        local_name!("meter")      => get_constructor!(HTMLMeterElementBinding),
+        local_name!("nav")        => get_constructor!(HTMLElementBinding),
+        local_name!("nobr")       => get_constructor!(HTMLElementBinding),
+        local_name!("noframes")   => get_constructor!(HTMLElementBinding),
+        local_name!("noscript")   => get_constructor!(HTMLElementBinding),
+        local_name!("object")     => get_constructor!(HTMLObjectElementBinding),
+        local_name!("ol")         => get_constructor!(HTMLOListElementBinding),
+        local_name!("optgroup")   => get_constructor!(HTMLOptGroupElementBinding),
+        local_name!("option")     => get_constructor!(HTMLOptionElementBinding),
+        local_name!("output")     => get_constructor!(HTMLOutputElementBinding),
+        local_name!("p")          => get_constructor!(HTMLParagraphElementBinding),
+        local_name!("param")      => get_constructor!(HTMLParamElementBinding),
+        local_name!("plaintext")  => get_constructor!(HTMLPreElementBinding),
+        local_name!("pre")        => get_constructor!(HTMLPreElementBinding),
+        local_name!("progress")   => get_constructor!(HTMLProgressElementBinding),
+        local_name!("q")          => get_constructor!(HTMLQuoteElementBinding),
+        local_name!("rp")         => get_constructor!(HTMLElementBinding),
+        local_name!("rt")         => get_constructor!(HTMLElementBinding),
+        local_name!("ruby")       => get_constructor!(HTMLElementBinding),
+        local_name!("s")          => get_constructor!(HTMLElementBinding),
+        local_name!("samp")       => get_constructor!(HTMLElementBinding),
+        local_name!("script")     => get_constructor!(HTMLScriptElementBinding),
+        local_name!("section")    => get_constructor!(HTMLElementBinding),
+        local_name!("select")     => get_constructor!(HTMLSelectElementBinding),
+        local_name!("small")      => get_constructor!(HTMLElementBinding),
+        local_name!("source")     => get_constructor!(HTMLSourceElementBinding),
+        local_name!("span")       => get_constructor!(HTMLSpanElementBinding),
+        local_name!("strike")     => get_constructor!(HTMLElementBinding),
+        local_name!("strong")     => get_constructor!(HTMLElementBinding),
+        local_name!("style")      => get_constructor!(HTMLStyleElementBinding),
+        local_name!("sub")        => get_constructor!(HTMLElementBinding),
+        local_name!("summary")    => get_constructor!(HTMLElementBinding),
+        local_name!("sup")        => get_constructor!(HTMLElementBinding),
+        local_name!("table")      => get_constructor!(HTMLTableElementBinding),
+        local_name!("tbody")      => get_constructor!(HTMLTableSectionElementBinding),
+        local_name!("td")         => get_constructor!(HTMLTableDataCellElementBinding),
+        local_name!("template")   => get_constructor!(HTMLTemplateElementBinding),
+        local_name!("textarea")   => get_constructor!(HTMLTextAreaElementBinding),
+        local_name!("tfoot")      => get_constructor!(HTMLTableSectionElementBinding),
+        local_name!("th")         => get_constructor!(HTMLTableHeaderCellElementBinding),
+        local_name!("thead")      => get_constructor!(HTMLTableSectionElementBinding),
+        local_name!("time")       => get_constructor!(HTMLTimeElementBinding),
+        local_name!("title")      => get_constructor!(HTMLTitleElementBinding),
+        local_name!("tr")         => get_constructor!(HTMLTableRowElementBinding),
+        local_name!("tt")         => get_constructor!(HTMLElementBinding),
+        local_name!("track")      => get_constructor!(HTMLTrackElementBinding),
+        local_name!("u")          => get_constructor!(HTMLElementBinding),
+        local_name!("ul")         => get_constructor!(HTMLUListElementBinding),
+        local_name!("var")        => get_constructor!(HTMLElementBinding),
+        local_name!("video")      => get_constructor!(HTMLVideoElementBinding),
+        local_name!("wbr")        => get_constructor!(HTMLElementBinding),
+        local_name!("xmp")        => get_constructor!(HTMLPreElementBinding),
+        _                         => false,
+    }
+}

components/script/dom/create.rs

@@ -111,6 +111,14 @@ fn create_html_element(name: QualName,
                        document: &Document,
                        creator: ElementCreator)
                        -> Root<Element> {
+    create_native_html_element(name, prefix, document, creator)
+}
+
+pub fn create_native_html_element(name: QualName,
+                                  prefix: Option<Prefix>,
+                                  document: &Document,
+                                  creator: ElementCreator)
+                                  -> Root<Element> {
     assert!(name.ns == ns!(html));
 
     macro_rules! make(

components/script/dom/customelementregistry.rs

@@ -18,6 +18,7 @@ use dom::globalscope::GlobalScope;
 use dom::promise::Promise;
 use dom::window::Window;
 use dom_struct::dom_struct;
+use html5ever::LocalName;
 use js::conversions::ToJSValConvertible;
 use js::jsapi::{IsConstructor, HandleObject, JS_GetProperty, JSAutoCompartment, JSContext};
 use js::jsval::{JSVal, UndefinedValue};
@@ -25,7 +26,7 @@ use std::cell::Cell;
 use std::collections::HashMap;
 use std::rc::Rc;
 
-// https://html.spec.whatwg.org/multipage/#customelementregistry
+/// https://html.spec.whatwg.org/multipage/#customelementregistry
 #[dom_struct]
 pub struct CustomElementRegistry {
     reflector_: Reflector,
@@ -37,7 +38,8 @@ pub struct CustomElementRegistry {
 
     element_definition_is_running: Cell<bool>,
 
-    definitions: DOMRefCell<HashMap<DOMString, CustomElementDefinition>>,
+    #[ignore_heap_size_of = "Rc"]
+    definitions: DOMRefCell<HashMap<DOMString, Rc<CustomElementDefinition>>>,
 }
 
 impl CustomElementRegistry {
@@ -57,14 +59,20 @@ impl CustomElementRegistry {
                            CustomElementRegistryBinding::Wrap)
     }
 
-    // Cleans up any active promises
+    /// Cleans up any active promises
-    // https://github.com/servo/servo/issues/15318
+    /// https://github.com/servo/servo/issues/15318
     pub fn teardown(&self) {
         self.when_defined.borrow_mut().clear()
     }
 
-    // https://html.spec.whatwg.org/multipage/#dom-customelementregistry-define
+    pub fn lookup_definition_by_constructor(&self, constructor: HandleObject) -> Option<Rc<CustomElementDefinition>> {
-    // Steps 10.1, 10.2
+        self.definitions.borrow().values().find(|definition| {
+            definition.constructor.callback() == constructor.get()
+        }).cloned()
+    }
+
+    /// https://html.spec.whatwg.org/multipage/#dom-customelementregistry-define
+    /// Steps 10.1, 10.2
     #[allow(unsafe_code)]
     fn check_prototype(&self, constructor: HandleObject) -> ErrorResult {
         let global_scope = self.window.upcast::<GlobalScope>();
@@ -89,7 +97,7 @@ impl CustomElementRegistry {
 
 impl CustomElementRegistryMethods for CustomElementRegistry {
     #[allow(unsafe_code, unrooted_must_root)]
-    // https://html.spec.whatwg.org/multipage/#dom-customelementregistry-define
+    /// https://html.spec.whatwg.org/multipage/#dom-customelementregistry-define
     fn Define(&self, name: DOMString, constructor_: Rc<Function>, options: &ElementDefinitionOptions) -> ErrorResult {
         let global_scope = self.window.upcast::<GlobalScope>();
         rooted!(in(global_scope.get_cx()) let constructor = constructor_.callback());
@@ -125,14 +133,14 @@ impl CustomElementRegistryMethods for CustomElementRegistry {
             }
 
             // Step 7.2
-            if !is_known_element_interface(extended_name) {
+            if !is_extendable_element_interface(extended_name) {
                 return Err(Error::NotSupported)
             }
 
-            extended_name.clone()
+            extended_name
         } else {
             // Step 7.3
-            name.clone()
+            &name
         };
 
         // Step 8
@@ -157,10 +165,12 @@ impl CustomElementRegistryMethods for CustomElementRegistry {
         result?;
 
         // Step 11
-        let definition = CustomElementDefinition::new(name.clone(), local_name, constructor_);
+        let definition = CustomElementDefinition::new(LocalName::from(&*name),
+                                                      LocalName::from(&**local_name),
+                                                      constructor_);
 
         // Step 12
-        self.definitions.borrow_mut().insert(name.clone(), definition);
+        self.definitions.borrow_mut().insert(name.clone(), Rc::new(definition));
 
         // TODO: Step 13, 14, 15
         // Handle custom element upgrades
@@ -175,7 +185,7 @@ impl CustomElementRegistryMethods for CustomElementRegistry {
         Ok(())
     }
 
-    // https://html.spec.whatwg.org/multipage/#dom-customelementregistry-get
+    /// https://html.spec.whatwg.org/multipage/#dom-customelementregistry-get
     #[allow(unsafe_code)]
     unsafe fn Get(&self, cx: *mut JSContext, name: DOMString) -> JSVal {
         match self.definitions.borrow().get(&name) {
@@ -188,7 +198,7 @@ impl CustomElementRegistryMethods for CustomElementRegistry {
         }
     }
 
-    // https://html.spec.whatwg.org/multipage/#dom-customelementregistry-whendefined
+    /// https://html.spec.whatwg.org/multipage/#dom-customelementregistry-whendefined
     #[allow(unrooted_must_root)]
     fn WhenDefined(&self, name: DOMString) -> Rc<Promise> {
         let global_scope = self.window.upcast::<GlobalScope>();
@@ -222,27 +232,33 @@ impl CustomElementRegistryMethods for CustomElementRegistry {
     }
 }
 
-#[derive(HeapSizeOf, JSTraceable)]
+/// https://html.spec.whatwg.org/multipage/#custom-element-definition
-struct CustomElementDefinition {
+#[derive(HeapSizeOf, JSTraceable, Clone)]
-    name: DOMString,
+pub struct CustomElementDefinition {
+    pub name: LocalName,
 
-    local_name: DOMString,
+    pub local_name: LocalName,
 
     #[ignore_heap_size_of = "Rc"]
-    constructor: Rc<Function>,
+    pub constructor: Rc<Function>,
 }
 
 impl CustomElementDefinition {
-    fn new(name: DOMString, local_name: DOMString, constructor: Rc<Function>) -> CustomElementDefinition {
+    fn new(name: LocalName, local_name: LocalName, constructor: Rc<Function>) -> CustomElementDefinition {
         CustomElementDefinition {
             name: name,
             local_name: local_name,
             constructor: constructor,
         }
     }
+
+    /// https://html.spec.whatwg.org/multipage/#autonomous-custom-element
+    pub fn is_autonomous(&self) -> bool {
+        self.name == self.local_name
+    }
 }
 
-// https://html.spec.whatwg.org/multipage/#valid-custom-element-name
+/// https://html.spec.whatwg.org/multipage/#valid-custom-element-name
 fn is_valid_custom_element_name(name: &str) -> bool {
     // Custom elment names must match:
     // PotentialCustomElementName ::= [a-z] (PCENChar)* '-' (PCENChar)*
@@ -284,8 +300,8 @@ fn is_valid_custom_element_name(name: &str) -> bool {
     true
 }
 
-// Check if this character is a PCENChar
+/// Check if this character is a PCENChar
-// https://html.spec.whatwg.org/multipage/#prod-pcenchar
+/// https://html.spec.whatwg.org/multipage/#prod-pcenchar
 fn is_potential_custom_element_char(c: char) -> bool {
     c == '-' || c == '.' || c == '_' || c == '\u{B7}' ||
     (c >= '0' && c <= '9') ||
@@ -303,12 +319,11 @@ fn is_potential_custom_element_char(c: char) -> bool {
     (c >= '\u{10000}' && c <= '\u{EFFFF}')
 }
 
-fn is_known_element_interface(element: &str) -> bool {
+fn is_extendable_element_interface(element: &str) -> bool {
     element == "a" ||
     element == "abbr" ||
     element == "acronym" ||
     element == "address" ||
-    element == "applet" ||
     element == "area" ||
     element == "article" ||
     element == "aside" ||

components/script/dom/webidls/HTMLAnchorElement.webidl

@@ -11,6 +11,7 @@
  */
 
 // https://html.spec.whatwg.org/multipage/#htmlanchorelement
+[HTMLConstructor]
 interface HTMLAnchorElement : HTMLElement {
   attribute DOMString target;
   //       attribute DOMString download;

components/script/dom/webidls/HTMLAppletElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlappletelement
+// Note: intentionally not [HTMLConstructor]
 interface HTMLAppletElement : HTMLElement {
   //         attribute DOMString align;
   //         attribute DOMString alt;

components/script/dom/webidls/HTMLAreaElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlareaelement
+[HTMLConstructor]
 interface HTMLAreaElement : HTMLElement {
   //         attribute DOMString alt;
   //         attribute DOMString coords;

components/script/dom/webidls/HTMLAudioElement.webidl

@@ -3,5 +3,5 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlaudioelement
-//[NamedConstructor=Audio(optional DOMString src)]
+[HTMLConstructor/*, NamedConstructor=Audio(optional DOMString src)*/]
 interface HTMLAudioElement : HTMLMediaElement {};

components/script/dom/webidls/HTMLBRElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlbrelement
+[HTMLConstructor]
 interface HTMLBRElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLBaseElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlbaseelement
+[HTMLConstructor]
 interface HTMLBaseElement : HTMLElement {
            attribute DOMString href;
 //           attribute DOMString target;

components/script/dom/webidls/HTMLBodyElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#the-body-element
+[HTMLConstructor]
 interface HTMLBodyElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLButtonElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlbuttonelement
+[HTMLConstructor]
 interface HTMLButtonElement : HTMLElement {
   //         attribute boolean autofocus;
              attribute boolean disabled;

components/script/dom/webidls/HTMLCanvasElement.webidl

@@ -5,6 +5,7 @@
 // https://html.spec.whatwg.org/multipage/#htmlcanvaselement
 typedef (CanvasRenderingContext2D or WebGLRenderingContext) RenderingContext;
 
+[HTMLConstructor]
 interface HTMLCanvasElement : HTMLElement {
   [Pure]
            attribute unsigned long width;

components/script/dom/webidls/HTMLDListElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmldlistelement
+[HTMLConstructor]
 interface HTMLDListElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLDataElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmldataelement
+[HTMLConstructor]
 interface HTMLDataElement : HTMLElement {
            attribute DOMString value;
 };

components/script/dom/webidls/HTMLDataListElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmldatalistelement
+[HTMLConstructor]
 interface HTMLDataListElement : HTMLElement {
   readonly attribute HTMLCollection options;
 };

components/script/dom/webidls/HTMLDetailsElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmldetailselement
+[HTMLConstructor]
 interface HTMLDetailsElement : HTMLElement {
     attribute boolean open;
 };

components/script/dom/webidls/HTMLDialogElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmldialogelement
+[HTMLConstructor]
 interface HTMLDialogElement : HTMLElement {
   attribute boolean open;
   attribute DOMString returnValue;

components/script/dom/webidls/HTMLDirectoryElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmldirectoryelement
+[HTMLConstructor]
 interface HTMLDirectoryElement : HTMLElement {
   //         attribute boolean compact;
 };

components/script/dom/webidls/HTMLDivElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmldivelement
+[HTMLConstructor]
 interface HTMLDivElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlelement
+[HTMLConstructor]
 interface HTMLElement : Element {
   // metadata attributes
            attribute DOMString title;

components/script/dom/webidls/HTMLEmbedElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlembedelement
+[HTMLConstructor]
 interface HTMLEmbedElement : HTMLElement {
   //         attribute DOMString src;
   //         attribute DOMString type;

components/script/dom/webidls/HTMLFieldSetElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlfieldsetelement
+[HTMLConstructor]
 interface HTMLFieldSetElement : HTMLElement {
            attribute boolean disabled;
   readonly attribute HTMLFormElement? form;

components/script/dom/webidls/HTMLFontElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlfontelement
+[HTMLConstructor]
 interface HTMLFontElement : HTMLElement {
   [TreatNullAs=EmptyString] attribute DOMString color;
   attribute DOMString face;

components/script/dom/webidls/HTMLFormElement.webidl

@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlformelement
-//[OverrideBuiltins]
+[/*OverrideBuiltins, */HTMLConstructor]
 interface HTMLFormElement : HTMLElement {
            attribute DOMString acceptCharset;
            attribute DOMString action;

components/script/dom/webidls/HTMLFrameElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlframeelement
+[HTMLConstructor]
 interface HTMLFrameElement : HTMLElement {
   //         attribute DOMString name;
   //         attribute DOMString scrolling;

components/script/dom/webidls/HTMLFrameSetElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlframesetelement
+[HTMLConstructor]
 interface HTMLFrameSetElement : HTMLElement {
   //         attribute DOMString cols;
   //         attribute DOMString rows;

components/script/dom/webidls/HTMLHRElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlhrelement
+[HTMLConstructor]
 interface HTMLHRElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLHeadElement.webidl

@@ -3,4 +3,5 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlheadelement
+[HTMLConstructor]
 interface HTMLHeadElement : HTMLElement {};

components/script/dom/webidls/HTMLHeadingElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlheadingelement
+[HTMLConstructor]
 interface HTMLHeadingElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLHtmlElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlhtmlelement
+[HTMLConstructor]
 interface HTMLHtmlElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLIFrameElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmliframeelement
+[HTMLConstructor]
 interface HTMLIFrameElement : HTMLElement {
            attribute DOMString src;
   //         attribute DOMString srcdoc;

components/script/dom/webidls/HTMLImageElement.webidl

@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlimageelement
-[NamedConstructor=Image(optional unsigned long width, optional unsigned long height)]
+[HTMLConstructor, NamedConstructor=Image(optional unsigned long width, optional unsigned long height)]
 interface HTMLImageElement : HTMLElement {
            attribute DOMString alt;
            attribute DOMString src;

components/script/dom/webidls/HTMLInputElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlinputelement
+[HTMLConstructor]
 interface HTMLInputElement : HTMLElement {
            attribute DOMString accept;
            attribute DOMString alt;

components/script/dom/webidls/HTMLLIElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmllielement
+[HTMLConstructor]
 interface HTMLLIElement : HTMLElement {
   attribute long value;
 

components/script/dom/webidls/HTMLLabelElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmllabelelement
+[HTMLConstructor]
 interface HTMLLabelElement : HTMLElement {
   readonly attribute HTMLFormElement? form;
   attribute DOMString htmlFor;

components/script/dom/webidls/HTMLLegendElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmllegendelement
+[HTMLConstructor]
 interface HTMLLegendElement : HTMLElement {
   readonly attribute HTMLFormElement? form;
 

components/script/dom/webidls/HTMLLinkElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmllinkelement
+[HTMLConstructor]
 interface HTMLLinkElement : HTMLElement {
            attribute DOMString href;
            attribute DOMString? crossOrigin;

components/script/dom/webidls/HTMLMapElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlmapelement
+[HTMLConstructor]
 interface HTMLMapElement : HTMLElement {
   //         attribute DOMString name;
   //readonly attribute HTMLCollection areas;

components/script/dom/webidls/HTMLMetaElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlmetaelement
+[HTMLConstructor]
 interface HTMLMetaElement : HTMLElement {
              attribute DOMString name;
   //         attribute DOMString httpEquiv;

components/script/dom/webidls/HTMLMeterElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlmeterelement
+[HTMLConstructor]
 interface HTMLMeterElement : HTMLElement {
   //         attribute double value;
   //         attribute double min;

components/script/dom/webidls/HTMLModElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlmodelement
+[HTMLConstructor]
 interface HTMLModElement : HTMLElement {
   //         attribute DOMString cite;
   //         attribute DOMString dateTime;

components/script/dom/webidls/HTMLOListElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlolistelement
+[HTMLConstructor]
 interface HTMLOListElement : HTMLElement {
   //         attribute boolean reversed;
   //         attribute long start;

components/script/dom/webidls/HTMLObjectElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlobjectelement
+[HTMLConstructor]
 interface HTMLObjectElement : HTMLElement {
   //         attribute DOMString data;
            attribute DOMString type;

components/script/dom/webidls/HTMLOptGroupElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmloptgroupelement
+[HTMLConstructor]
 interface HTMLOptGroupElement : HTMLElement {
            attribute boolean disabled;
   //         attribute DOMString label;

components/script/dom/webidls/HTMLOptionElement.webidl

@@ -3,9 +3,9 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmloptionelement
-//[NamedConstructor=Option(optional DOMString text = "", optional DOMString value,
+[HTMLConstructor/*, NamedConstructor=Option(optional DOMString text = "", optional DOMString value,
-//                         optional boolean defaultSelected = false,
+                         optional boolean defaultSelected = false,
-//                         optional boolean selected = false)]
+                         optional boolean selected = false)*/]
 interface HTMLOptionElement : HTMLElement {
              attribute boolean disabled;
              readonly attribute HTMLFormElement? form;

components/script/dom/webidls/HTMLOutputElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmloutputelement
+[HTMLConstructor]
 interface HTMLOutputElement : HTMLElement {
   // [SameObject, PutForwards=value] readonly attribute DOMTokenList htmlFor;
   readonly attribute HTMLFormElement? form;

components/script/dom/webidls/HTMLParagraphElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlparagraphelement
+[HTMLConstructor]
 interface HTMLParagraphElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLParamElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlparamelement
+[HTMLConstructor]
 interface HTMLParamElement : HTMLElement {
   //         attribute DOMString name;
   //         attribute DOMString value;

components/script/dom/webidls/HTMLPreElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlpreelement
+[HTMLConstructor]
 interface HTMLPreElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLProgressElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlprogresselement
+[HTMLConstructor]
 interface HTMLProgressElement : HTMLElement {
   //         attribute double value;
   //         attribute double max;

components/script/dom/webidls/HTMLQuoteElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlquoteelement
+[HTMLConstructor]
 interface HTMLQuoteElement : HTMLElement {
   //         attribute DOMString cite;
 };

components/script/dom/webidls/HTMLScriptElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlscriptelement
+[HTMLConstructor]
 interface HTMLScriptElement : HTMLElement {
            attribute DOMString src;
            attribute DOMString type;

components/script/dom/webidls/HTMLSelectElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlselectelement
+[HTMLConstructor]
 interface HTMLSelectElement : HTMLElement {
   //         attribute boolean autofocus;
            attribute boolean disabled;

components/script/dom/webidls/HTMLSourceElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlsourceelement
+[HTMLConstructor]
 interface HTMLSourceElement : HTMLElement {
   //         attribute DOMString src;
   //         attribute DOMString type;

components/script/dom/webidls/HTMLSpanElement.webidl

@@ -3,4 +3,5 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlspanelement
+[HTMLConstructor]
 interface HTMLSpanElement : HTMLElement {};

components/script/dom/webidls/HTMLStyleElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlstyleelement
+[HTMLConstructor]
 interface HTMLStyleElement : HTMLElement {
   //         attribute DOMString media;
   //         attribute DOMString type;

components/script/dom/webidls/HTMLTableCaptionElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltablecaptionelement
+[HTMLConstructor]
 interface HTMLTableCaptionElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLTableCellElement.webidl

@@ -3,7 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltablecellelement
-[Abstract]
+[HTMLConstructor, Abstract]
 interface HTMLTableCellElement : HTMLElement {
   attribute unsigned long colSpan;
   attribute unsigned long rowSpan;

components/script/dom/webidls/HTMLTableColElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltablecolelement
+[HTMLConstructor]
 interface HTMLTableColElement : HTMLElement {
   //         attribute unsigned long span;
 

components/script/dom/webidls/HTMLTableDataCellElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltabledatacellelement
+[HTMLConstructor]
 interface HTMLTableDataCellElement : HTMLTableCellElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLTableElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltableelement
+[HTMLConstructor]
 interface HTMLTableElement : HTMLElement {
            attribute HTMLTableCaptionElement? caption;
   HTMLTableCaptionElement createCaption();

components/script/dom/webidls/HTMLTableHeaderCellElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltableheadercellelement
+[HTMLConstructor]
 interface HTMLTableHeaderCellElement : HTMLTableCellElement {
   //         attribute DOMString scope;
   //         attribute DOMString abbr;

components/script/dom/webidls/HTMLTableRowElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltablerowelement
+[HTMLConstructor]
 interface HTMLTableRowElement : HTMLElement {
   readonly attribute long rowIndex;
   readonly attribute long sectionRowIndex;

components/script/dom/webidls/HTMLTableSectionElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltablesectionelement
+[HTMLConstructor]
 interface HTMLTableSectionElement : HTMLElement {
   readonly attribute HTMLCollection rows;
   [Throws]

components/script/dom/webidls/HTMLTemplateElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltemplateelement
+[HTMLConstructor]
 interface HTMLTemplateElement : HTMLElement {
   readonly attribute DocumentFragment content;
 };

components/script/dom/webidls/HTMLTextAreaElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltextareaelement
+[HTMLConstructor]
 interface HTMLTextAreaElement : HTMLElement {
   //         attribute DOMString autocomplete;
   //         attribute boolean autofocus;

components/script/dom/webidls/HTMLTimeElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltimeelement
+[HTMLConstructor]
 interface HTMLTimeElement : HTMLElement {
   attribute DOMString dateTime;
 };

components/script/dom/webidls/HTMLTitleElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltitleelement
+[HTMLConstructor]
 interface HTMLTitleElement : HTMLElement {
     [Pure]
            attribute DOMString text;

components/script/dom/webidls/HTMLTrackElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmltrackelement
+[HTMLConstructor]
 interface HTMLTrackElement : HTMLElement {
   //         attribute DOMString kind;
   //         attribute DOMString src;

components/script/dom/webidls/HTMLUListElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlulistelement
+[HTMLConstructor]
 interface HTMLUListElement : HTMLElement {
   // also has obsolete members
 };

components/script/dom/webidls/HTMLVideoElement.webidl

@@ -3,6 +3,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 // https://html.spec.whatwg.org/multipage/#htmlvideoelement
+[HTMLConstructor]
 interface HTMLVideoElement : HTMLMediaElement {
   //         attribute unsigned long width;
   //         attribute unsigned long height;

tests/wpt/metadata/MANIFEST.json

@@ -554120,7 +554120,7 @@
    "testharness"
   ],
   "custom-elements/HTMLElement-constructor.html": [
-   "7fefdaa4cbdf30c505858730a5a3858e9db5dbc2",
+   "64522527ef425b90c704b20b000c8feef0d1ca25",
    "testharness"
   ],
   "custom-elements/OWNERS": [

tests/wpt/metadata/custom-elements/CustomElementRegistry.html.ini

@@ -27,9 +27,6 @@
   [customElements.define must rethrow an exception thrown while retrieving Symbol.iterator on observedAttributes]
     expected: FAIL
 
-  [customElements.define must define an instantiatable custom element]
-    expected: FAIL
-
   [customElements.define must upgrade elements in the shadow-including tree order]
     expected: FAIL
 

tests/wpt/metadata/custom-elements/HTMLElement-constructor.html.ini

@@ -1,11 +0,0 @@
-[HTMLElement-constructor.html]
-  type: testharness
-  [HTMLElement constructor must infer the tag name from the element interface]
-    expected: FAIL
-
-  [HTMLElement constructor must allow subclassing a custom element]
-    expected: FAIL
-
-  [HTMLElement constructor must allow subclassing an user-defined subclass of HTMLElement]
-    expected: FAIL
-

tests/wpt/metadata/custom-elements/htmlconstructor/newtarget.html.ini

@@ -1,32 +0,0 @@
-[newtarget.html]
-  type: testharness
-  [Use NewTarget's prototype, not the one stored at definition time]
-    expected: FAIL
-
-  [Rethrow any exceptions thrown while getting the prototype]
-    expected: FAIL
-
-  [If prototype is not object (null), derives the fallback from NewTarget's realm (autonomous custom elements)]
-    expected: FAIL
-
-  [If prototype is not object (undefined), derives the fallback from NewTarget's realm (autonomous custom elements)]
-    expected: FAIL
-
-  [If prototype is not object (5), derives the fallback from NewTarget's realm (autonomous custom elements)]
-    expected: FAIL
-
-  [If prototype is not object (string), derives the fallback from NewTarget's realm (autonomous custom elements)]
-    expected: FAIL
-
-  [If prototype is not object (null), derives the fallback from NewTarget's realm (customized built-in elements)]
-    expected: FAIL
-
-  [If prototype is not object (undefined), derives the fallback from NewTarget's realm (customized built-in elements)]
-    expected: FAIL
-
-  [If prototype is not object (5), derives the fallback from NewTarget's realm (customized built-in elements)]
-    expected: FAIL
-
-  [If prototype is not object (string), derives the fallback from NewTarget's realm (customized built-in elements)]
-    expected: FAIL
-

tests/wpt/web-platform-tests/custom-elements/HTMLElement-constructor.html

@@ -27,6 +27,18 @@ test(function () {
     assert_throws({'name': 'TypeError'}, function () { new SomeCustomElement; });
 }, 'HTMLElement constructor must throw TypeError when it has not been defined by customElements.define');
 
+test(function () {
+    class SomeCustomElement extends HTMLParagraphElement {};
+    customElements.define('some-custom-element', SomeCustomElement);
+    assert_throws({'name': 'TypeError'}, function () { new SomeCustomElement(); });
+}, 'Custom element constructor must throw TypeError when it does not extend HTMLElement');
+
+test(function () {
+    class SomeCustomButtonElement extends HTMLButtonElement {};
+    customElements.define('some-custom-button-element', SomeCustomButtonElement, { extends: "p" });
+    assert_throws({'name': 'TypeError'}, function () { new SomeCustomButtonElement(); });
+}, 'Custom element constructor must throw TypeError when it does not extend the proper element interface');
+
 test(function () {
     class CustomElementWithInferredTagName extends HTMLElement {};
     customElements.define('inferred-name', CustomElementWithInferredTagName);