Merge remote-tracking branch 'upstream/master' into feat-cow-infra

`tests/wpt/web-platform-tests/html/browsers/origin/cross-origin-objects/cross-origin-objects.html`
was reverted to the upstream version.

1 files changed, 344 insertions, 238 deletions

diff --git a/components/script/dom/create.rs b/components/script/dom/create.rs
index 7c9a9eeea9c..37aaf07286f 100644
--- a/components/script/dom/create.rs
+++ b/components/script/dom/create.rs
@@ -1,290 +1,396 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
-use dom::bindings::js::Root;
-use dom::bindings::str::DOMString;
-use dom::document::Document;
-use dom::element::Element;
-use dom::element::ElementCreator;
-use dom::htmlanchorelement::HTMLAnchorElement;
-use dom::htmlappletelement::HTMLAppletElement;
-use dom::htmlareaelement::HTMLAreaElement;
-use dom::htmlaudioelement::HTMLAudioElement;
-use dom::htmlbaseelement::HTMLBaseElement;
-use dom::htmlbodyelement::HTMLBodyElement;
-use dom::htmlbrelement::HTMLBRElement;
-use dom::htmlbuttonelement::HTMLButtonElement;
-use dom::htmlcanvaselement::HTMLCanvasElement;
-use dom::htmldataelement::HTMLDataElement;
-use dom::htmldatalistelement::HTMLDataListElement;
-use dom::htmldetailselement::HTMLDetailsElement;
-use dom::htmldialogelement::HTMLDialogElement;
-use dom::htmldirectoryelement::HTMLDirectoryElement;
-use dom::htmldivelement::HTMLDivElement;
-use dom::htmldlistelement::HTMLDListElement;
-use dom::htmlelement::HTMLElement;
-use dom::htmlembedelement::HTMLEmbedElement;
-use dom::htmlfieldsetelement::HTMLFieldSetElement;
-use dom::htmlfontelement::HTMLFontElement;
-use dom::htmlformelement::HTMLFormElement;
-use dom::htmlframeelement::HTMLFrameElement;
-use dom::htmlframesetelement::HTMLFrameSetElement;
-use dom::htmlheadelement::HTMLHeadElement;
-use dom::htmlheadingelement::HTMLHeadingElement;
-use dom::htmlheadingelement::HeadingLevel;
-use dom::htmlhrelement::HTMLHRElement;
-use dom::htmlhtmlelement::HTMLHtmlElement;
-use dom::htmliframeelement::HTMLIFrameElement;
-use dom::htmlimageelement::HTMLImageElement;
-use dom::htmlinputelement::HTMLInputElement;
-use dom::htmllabelelement::HTMLLabelElement;
-use dom::htmllegendelement::HTMLLegendElement;
-use dom::htmllielement::HTMLLIElement;
-use dom::htmllinkelement::HTMLLinkElement;
-use dom::htmlmapelement::HTMLMapElement;
-use dom::htmlmetaelement::HTMLMetaElement;
-use dom::htmlmeterelement::HTMLMeterElement;
-use dom::htmlmodelement::HTMLModElement;
-use dom::htmlobjectelement::HTMLObjectElement;
-use dom::htmlolistelement::HTMLOListElement;
-use dom::htmloptgroupelement::HTMLOptGroupElement;
-use dom::htmloptionelement::HTMLOptionElement;
-use dom::htmloutputelement::HTMLOutputElement;
-use dom::htmlparagraphelement::HTMLParagraphElement;
-use dom::htmlparamelement::HTMLParamElement;
-use dom::htmlpreelement::HTMLPreElement;
-use dom::htmlprogresselement::HTMLProgressElement;
-use dom::htmlquoteelement::HTMLQuoteElement;
-use dom::htmlscriptelement::HTMLScriptElement;
-use dom::htmlselectelement::HTMLSelectElement;
-use dom::htmlsourceelement::HTMLSourceElement;
-use dom::htmlspanelement::HTMLSpanElement;
-use dom::htmlstyleelement::HTMLStyleElement;
-use dom::htmltablecaptionelement::HTMLTableCaptionElement;
-use dom::htmltablecolelement::HTMLTableColElement;
-use dom::htmltabledatacellelement::HTMLTableDataCellElement;
-use dom::htmltableelement::HTMLTableElement;
-use dom::htmltableheadercellelement::HTMLTableHeaderCellElement;
-use dom::htmltablerowelement::HTMLTableRowElement;
-use dom::htmltablesectionelement::HTMLTableSectionElement;
-use dom::htmltemplateelement::HTMLTemplateElement;
-use dom::htmltextareaelement::HTMLTextAreaElement;
-use dom::htmltimeelement::HTMLTimeElement;
-use dom::htmltitleelement::HTMLTitleElement;
-use dom::htmltrackelement::HTMLTrackElement;
-use dom::htmlulistelement::HTMLUListElement;
-use dom::htmlunknownelement::HTMLUnknownElement;
-use dom::htmlvideoelement::HTMLVideoElement;
-use dom::svgsvgelement::SVGSVGElement;
-use html5ever_atoms::{Prefix, QualName};
-use servo_config::prefs::PREFS;
+use crate::dom::bindings::error::{report_pending_exception, throw_dom_exception};
+use crate::dom::bindings::reflector::DomObject;
+use crate::dom::bindings::root::DomRoot;
+use crate::dom::customelementregistry::{
+    is_valid_custom_element_name, upgrade_element, CustomElementState,
+};
+use crate::dom::document::Document;
+use crate::dom::element::{CustomElementCreationMode, Element, ElementCreator};
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::htmlanchorelement::HTMLAnchorElement;
+use crate::dom::htmlareaelement::HTMLAreaElement;
+use crate::dom::htmlaudioelement::HTMLAudioElement;
+use crate::dom::htmlbaseelement::HTMLBaseElement;
+use crate::dom::htmlbodyelement::HTMLBodyElement;
+use crate::dom::htmlbrelement::HTMLBRElement;
+use crate::dom::htmlbuttonelement::HTMLButtonElement;
+use crate::dom::htmlcanvaselement::HTMLCanvasElement;
+use crate::dom::htmldataelement::HTMLDataElement;
+use crate::dom::htmldatalistelement::HTMLDataListElement;
+use crate::dom::htmldetailselement::HTMLDetailsElement;
+use crate::dom::htmldialogelement::HTMLDialogElement;
+use crate::dom::htmldirectoryelement::HTMLDirectoryElement;
+use crate::dom::htmldivelement::HTMLDivElement;
+use crate::dom::htmldlistelement::HTMLDListElement;
+use crate::dom::htmlelement::HTMLElement;
+use crate::dom::htmlembedelement::HTMLEmbedElement;
+use crate::dom::htmlfieldsetelement::HTMLFieldSetElement;
+use crate::dom::htmlfontelement::HTMLFontElement;
+use crate::dom::htmlformelement::HTMLFormElement;
+use crate::dom::htmlframeelement::HTMLFrameElement;
+use crate::dom::htmlframesetelement::HTMLFrameSetElement;
+use crate::dom::htmlheadelement::HTMLHeadElement;
+use crate::dom::htmlheadingelement::HTMLHeadingElement;
+use crate::dom::htmlheadingelement::HeadingLevel;
+use crate::dom::htmlhrelement::HTMLHRElement;
+use crate::dom::htmlhtmlelement::HTMLHtmlElement;
+use crate::dom::htmliframeelement::HTMLIFrameElement;
+use crate::dom::htmlimageelement::HTMLImageElement;
+use crate::dom::htmlinputelement::HTMLInputElement;
+use crate::dom::htmllabelelement::HTMLLabelElement;
+use crate::dom::htmllegendelement::HTMLLegendElement;
+use crate::dom::htmllielement::HTMLLIElement;
+use crate::dom::htmllinkelement::HTMLLinkElement;
+use crate::dom::htmlmapelement::HTMLMapElement;
+use crate::dom::htmlmenuelement::HTMLMenuElement;
+use crate::dom::htmlmetaelement::HTMLMetaElement;
+use crate::dom::htmlmeterelement::HTMLMeterElement;
+use crate::dom::htmlmodelement::HTMLModElement;
+use crate::dom::htmlobjectelement::HTMLObjectElement;
+use crate::dom::htmlolistelement::HTMLOListElement;
+use crate::dom::htmloptgroupelement::HTMLOptGroupElement;
+use crate::dom::htmloptionelement::HTMLOptionElement;
+use crate::dom::htmloutputelement::HTMLOutputElement;
+use crate::dom::htmlparagraphelement::HTMLParagraphElement;
+use crate::dom::htmlparamelement::HTMLParamElement;
+use crate::dom::htmlpictureelement::HTMLPictureElement;
+use crate::dom::htmlpreelement::HTMLPreElement;
+use crate::dom::htmlprogresselement::HTMLProgressElement;
+use crate::dom::htmlquoteelement::HTMLQuoteElement;
+use crate::dom::htmlscriptelement::HTMLScriptElement;
+use crate::dom::htmlselectelement::HTMLSelectElement;
+use crate::dom::htmlsourceelement::HTMLSourceElement;
+use crate::dom::htmlspanelement::HTMLSpanElement;
+use crate::dom::htmlstyleelement::HTMLStyleElement;
+use crate::dom::htmltablecaptionelement::HTMLTableCaptionElement;
+use crate::dom::htmltablecellelement::HTMLTableCellElement;
+use crate::dom::htmltablecolelement::HTMLTableColElement;
+use crate::dom::htmltableelement::HTMLTableElement;
+use crate::dom::htmltablerowelement::HTMLTableRowElement;
+use crate::dom::htmltablesectionelement::HTMLTableSectionElement;
+use crate::dom::htmltemplateelement::HTMLTemplateElement;
+use crate::dom::htmltextareaelement::HTMLTextAreaElement;
+use crate::dom::htmltimeelement::HTMLTimeElement;
+use crate::dom::htmltitleelement::HTMLTitleElement;
+use crate::dom::htmltrackelement::HTMLTrackElement;
+use crate::dom::htmlulistelement::HTMLUListElement;
+use crate::dom::htmlunknownelement::HTMLUnknownElement;
+use crate::dom::htmlvideoelement::HTMLVideoElement;
+use crate::dom::svgelement::SVGElement;
+use crate::dom::svgsvgelement::SVGSVGElement;
+use crate::realms::{enter_realm, InRealm};
+use crate::script_thread::ScriptThread;
+use html5ever::{LocalName, Prefix, QualName};
+use servo_config::pref;
 
-fn create_svg_element(name: QualName,
-                      prefix: Option<DOMString>,
-                      document: &Document)
-                      -> Root<Element> {
-    assert!(name.ns == ns!(svg));
+fn create_svg_element(
+    name: QualName,
+    prefix: Option<Prefix>,
+    document: &Document,
+) -> DomRoot<Element> {
+    assert_eq!(name.ns, ns!(svg));
 
     macro_rules! make(
         ($ctor:ident) => ({
             let obj = $ctor::new(name.local, prefix, document);
-            Root::upcast(obj)
+            DomRoot::upcast(obj)
         });
         ($ctor:ident, $($arg:expr),+) => ({
             let obj = $ctor::new(name.local, prefix, document, $($arg),+);
-            Root::upcast(obj)
+            DomRoot::upcast(obj)
         })
     );
 
-    if !PREFS.get("dom.svg.enabled").as_boolean().unwrap_or(false) {
+    if !pref!(dom.svg.enabled) {
         return Element::new(name.local, name.ns, prefix, document);
     }
 
     match name.local {
-        local_name!("svg")        => make!(SVGSVGElement),
-        _                   => Element::new(name.local, name.ns, prefix, document),
+        local_name!("svg") => make!(SVGSVGElement),
+        _ => make!(SVGElement),
     }
 }
 
-fn create_html_element(name: QualName,
-                      prefix: Option<DOMString>,
-                      document: &Document,
-                      creator: ElementCreator)
-                      -> Root<Element> {
-    assert!(name.ns == ns!(html));
+// https://dom.spec.whatwg.org/#concept-create-element
+#[allow(unsafe_code)]
+fn create_html_element(
+    name: QualName,
+    prefix: Option<Prefix>,
+    is: Option<LocalName>,
+    document: &Document,
+    creator: ElementCreator,
+    mode: CustomElementCreationMode,
+) -> DomRoot<Element> {
+    assert_eq!(name.ns, ns!(html));
+
+    // Step 4
+    let definition = document.lookup_custom_element_definition(&name.ns, &name.local, is.as_ref());
+
+    if let Some(definition) = definition {
+        if definition.is_autonomous() {
+            match mode {
+                CustomElementCreationMode::Asynchronous => {
+                    let result = DomRoot::upcast::<Element>(HTMLElement::new(
+                        name.local.clone(),
+                        prefix.clone(),
+                        document,
+                    ));
+                    result.set_custom_element_state(CustomElementState::Undefined);
+                    ScriptThread::enqueue_upgrade_reaction(&*result, definition);
+                    return result;
+                },
+                CustomElementCreationMode::Synchronous => {
+                    let local_name = name.local.clone();
+                    return match definition.create_element(document, prefix.clone()) {
+                        Ok(element) => {
+                            element.set_custom_element_definition(definition.clone());
+                            element
+                        },
+                        Err(error) => {
+                            // Step 6. Recovering from exception.
+                            let global =
+                                GlobalScope::current().unwrap_or_else(|| document.global());
+                            let cx = global.get_cx();
+
+                            // Step 6.1.1
+                            unsafe {
+                                let ar = enter_realm(&*global);
+                                throw_dom_exception(cx, &global, error);
+                                report_pending_exception(*cx, true, InRealm::Entered(&ar));
+                            }
+
+                            // Step 6.1.2
+                            let element = DomRoot::upcast::<Element>(HTMLUnknownElement::new(
+                                local_name, prefix, document,
+                            ));
+                            element.set_custom_element_state(CustomElementState::Failed);
+                            element
+                        },
+                    };
+                },
+            }
+        } else {
+            // Steps 5.1-5.2
+            let element = create_native_html_element(name, prefix, document, creator);
+            element.set_is(definition.name.clone());
+            element.set_custom_element_state(CustomElementState::Undefined);
+            match mode {
+                // Step 5.3
+                CustomElementCreationMode::Synchronous => upgrade_element(definition, &*element),
+                // Step 5.4
+                CustomElementCreationMode::Asynchronous => {
+                    ScriptThread::enqueue_upgrade_reaction(&*element, definition)
+                },
+            }
+            return element;
+        }
+    }
+
+    // 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);
+            } else {
+                result.set_custom_element_state(CustomElementState::Uncustomized);
+            }
+        },
+    };
+
+    // Step 8
+    result
+}
+
+pub fn create_native_html_element(
+    name: QualName,
+    prefix: Option<Prefix>,
+    document: &Document,
+    creator: ElementCreator,
+) -> DomRoot<Element> {
+    assert_eq!(name.ns, ns!(html));
 
     macro_rules! make(
         ($ctor:ident) => ({
             let obj = $ctor::new(name.local, prefix, document);
-            Root::upcast(obj)
+            DomRoot::upcast(obj)
         });
         ($ctor:ident, $($arg:expr),+) => ({
             let obj = $ctor::new(name.local, prefix, document, $($arg),+);
-            Root::upcast(obj)
+            DomRoot::upcast(obj)
         })
     );
 
     // This is a big match, and the IDs for inline-interned atoms are not very structured.
     // Perhaps we should build a perfect hash from those IDs instead.
+    // https://html.spec.whatwg.org/multipage/#elements-in-the-dom
     match name.local {
-        local_name!("a")          => make!(HTMLAnchorElement),
-        local_name!("abbr")       => make!(HTMLElement),
-        local_name!("acronym")    => make!(HTMLElement),
-        local_name!("address")    => make!(HTMLElement),
-        local_name!("applet")     => make!(HTMLAppletElement),
-        local_name!("area")       => make!(HTMLAreaElement),
-        local_name!("article")    => make!(HTMLElement),
-        local_name!("aside")      => make!(HTMLElement),
-        local_name!("audio")      => make!(HTMLAudioElement),
-        local_name!("b")          => make!(HTMLElement),
-        local_name!("base")       => make!(HTMLBaseElement),
-        local_name!("bdi")        => make!(HTMLElement),
-        local_name!("bdo")        => make!(HTMLElement),
+        local_name!("a") => make!(HTMLAnchorElement),
+        local_name!("abbr") => make!(HTMLElement),
+        local_name!("acronym") => make!(HTMLElement),
+        local_name!("address") => make!(HTMLElement),
+        local_name!("area") => make!(HTMLAreaElement),
+        local_name!("article") => make!(HTMLElement),
+        local_name!("aside") => make!(HTMLElement),
+        local_name!("audio") => make!(HTMLAudioElement),
+        local_name!("b") => make!(HTMLElement),
+        local_name!("base") => make!(HTMLBaseElement),
+        local_name!("bdi") => make!(HTMLElement),
+        local_name!("bdo") => make!(HTMLElement),
         // https://html.spec.whatwg.org/multipage/#other-elements,-attributes-and-apis:bgsound
-        local_name!("bgsound")    => make!(HTMLUnknownElement),
-        local_name!("big")        => make!(HTMLElement),
+        local_name!("bgsound") => make!(HTMLUnknownElement),
+        local_name!("big") => make!(HTMLElement),
         // https://html.spec.whatwg.org/multipage/#other-elements,-attributes-and-apis:blink
-        local_name!("blink")      => make!(HTMLUnknownElement),
+        local_name!("blink") => make!(HTMLUnknownElement),
         // https://html.spec.whatwg.org/multipage/#the-blockquote-element
         local_name!("blockquote") => make!(HTMLQuoteElement),
-        local_name!("body")       => make!(HTMLBodyElement),
-        local_name!("br")         => make!(HTMLBRElement),
-        local_name!("button")     => make!(HTMLButtonElement),
-        local_name!("canvas")     => make!(HTMLCanvasElement),
-        local_name!("caption")    => make!(HTMLTableCaptionElement),
-        local_name!("center")     => make!(HTMLElement),
-        local_name!("cite")       => make!(HTMLElement),
-        local_name!("code")       => make!(HTMLElement),
-        local_name!("col")        => make!(HTMLTableColElement),
-        local_name!("colgroup")   => make!(HTMLTableColElement),
-        local_name!("data")       => make!(HTMLDataElement),
-        local_name!("datalist")   => make!(HTMLDataListElement),
-        local_name!("dd")         => make!(HTMLElement),
-        local_name!("del")        => make!(HTMLModElement),
-        local_name!("details")    => make!(HTMLDetailsElement),
-        local_name!("dfn")        => make!(HTMLElement),
-        local_name!("dialog")     => make!(HTMLDialogElement),
-        local_name!("dir")        => make!(HTMLDirectoryElement),
-        local_name!("div")        => make!(HTMLDivElement),
-        local_name!("dl")         => make!(HTMLDListElement),
-        local_name!("dt")         => make!(HTMLElement),
-        local_name!("em")         => make!(HTMLElement),
-        local_name!("embed")      => make!(HTMLEmbedElement),
-        local_name!("fieldset")   => make!(HTMLFieldSetElement),
+        local_name!("body") => make!(HTMLBodyElement),
+        local_name!("br") => make!(HTMLBRElement),
+        local_name!("button") => make!(HTMLButtonElement),
+        local_name!("canvas") => make!(HTMLCanvasElement),
+        local_name!("caption") => make!(HTMLTableCaptionElement),
+        local_name!("center") => make!(HTMLElement),
+        local_name!("cite") => make!(HTMLElement),
+        local_name!("code") => make!(HTMLElement),
+        local_name!("col") => make!(HTMLTableColElement),
+        local_name!("colgroup") => make!(HTMLTableColElement),
+        local_name!("data") => make!(HTMLDataElement),
+        local_name!("datalist") => make!(HTMLDataListElement),
+        local_name!("dd") => make!(HTMLElement),
+        local_name!("del") => make!(HTMLModElement),
+        local_name!("details") => make!(HTMLDetailsElement),
+        local_name!("dfn") => make!(HTMLElement),
+        local_name!("dialog") => make!(HTMLDialogElement),
+        local_name!("dir") => make!(HTMLDirectoryElement),
+        local_name!("div") => make!(HTMLDivElement),
+        local_name!("dl") => make!(HTMLDListElement),
+        local_name!("dt") => make!(HTMLElement),
+        local_name!("em") => make!(HTMLElement),
+        local_name!("embed") => make!(HTMLEmbedElement),
+        local_name!("fieldset") => make!(HTMLFieldSetElement),
         local_name!("figcaption") => make!(HTMLElement),
-        local_name!("figure")     => make!(HTMLElement),
-        local_name!("font")       => make!(HTMLFontElement),
-        local_name!("footer")     => make!(HTMLElement),
-        local_name!("form")       => make!(HTMLFormElement),
-        local_name!("frame")      => make!(HTMLFrameElement),
-        local_name!("frameset")   => make!(HTMLFrameSetElement),
-        local_name!("h1")         => make!(HTMLHeadingElement, HeadingLevel::Heading1),
-        local_name!("h2")         => make!(HTMLHeadingElement, HeadingLevel::Heading2),
-        local_name!("h3")         => make!(HTMLHeadingElement, HeadingLevel::Heading3),
-        local_name!("h4")         => make!(HTMLHeadingElement, HeadingLevel::Heading4),
-        local_name!("h5")         => make!(HTMLHeadingElement, HeadingLevel::Heading5),
-        local_name!("h6")         => make!(HTMLHeadingElement, HeadingLevel::Heading6),
-        local_name!("head")       => make!(HTMLHeadElement),
-        local_name!("header")     => make!(HTMLElement),
-        local_name!("hgroup")     => make!(HTMLElement),
-        local_name!("hr")         => make!(HTMLHRElement),
-        local_name!("html")       => make!(HTMLHtmlElement),
-        local_name!("i")          => make!(HTMLElement),
-        local_name!("iframe")     => make!(HTMLIFrameElement),
-        local_name!("img")        => make!(HTMLImageElement),
-        local_name!("input")      => make!(HTMLInputElement),
-        local_name!("ins")        => make!(HTMLModElement),
+        local_name!("figure") => make!(HTMLElement),
+        local_name!("font") => make!(HTMLFontElement),
+        local_name!("footer") => make!(HTMLElement),
+        local_name!("form") => make!(HTMLFormElement),
+        local_name!("frame") => make!(HTMLFrameElement),
+        local_name!("frameset") => make!(HTMLFrameSetElement),
+        local_name!("h1") => make!(HTMLHeadingElement, HeadingLevel::Heading1),
+        local_name!("h2") => make!(HTMLHeadingElement, HeadingLevel::Heading2),
+        local_name!("h3") => make!(HTMLHeadingElement, HeadingLevel::Heading3),
+        local_name!("h4") => make!(HTMLHeadingElement, HeadingLevel::Heading4),
+        local_name!("h5") => make!(HTMLHeadingElement, HeadingLevel::Heading5),
+        local_name!("h6") => make!(HTMLHeadingElement, HeadingLevel::Heading6),
+        local_name!("head") => make!(HTMLHeadElement),
+        local_name!("header") => make!(HTMLElement),
+        local_name!("hgroup") => make!(HTMLElement),
+        local_name!("hr") => make!(HTMLHRElement),
+        local_name!("html") => make!(HTMLHtmlElement),
+        local_name!("i") => make!(HTMLElement),
+        local_name!("iframe") => make!(HTMLIFrameElement),
+        local_name!("img") => make!(HTMLImageElement),
+        local_name!("input") => make!(HTMLInputElement),
+        local_name!("ins") => make!(HTMLModElement),
         // https://html.spec.whatwg.org/multipage/#other-elements,-attributes-and-apis:isindex-2
-        local_name!("isindex")    => make!(HTMLUnknownElement),
-        local_name!("kbd")        => make!(HTMLElement),
-        local_name!("label")      => make!(HTMLLabelElement),
-        local_name!("legend")     => make!(HTMLLegendElement),
-        local_name!("li")         => make!(HTMLLIElement),
-        local_name!("link")       => make!(HTMLLinkElement, creator),
+        local_name!("isindex") => make!(HTMLUnknownElement),
+        local_name!("kbd") => make!(HTMLElement),
+        local_name!("label") => make!(HTMLLabelElement),
+        local_name!("legend") => make!(HTMLLegendElement),
+        local_name!("li") => make!(HTMLLIElement),
+        local_name!("link") => make!(HTMLLinkElement, creator),
         // https://html.spec.whatwg.org/multipage/#other-elements,-attributes-and-apis:listing
-        local_name!("listing")    => make!(HTMLPreElement),
-        local_name!("main")       => make!(HTMLElement),
-        local_name!("map")        => make!(HTMLMapElement),
-        local_name!("mark")       => make!(HTMLElement),
-        local_name!("marquee")    => make!(HTMLElement),
-        local_name!("meta")       => make!(HTMLMetaElement),
-        local_name!("meter")      => make!(HTMLMeterElement),
+        local_name!("listing") => make!(HTMLPreElement),
+        local_name!("main") => make!(HTMLElement),
+        local_name!("map") => make!(HTMLMapElement),
+        local_name!("mark") => make!(HTMLElement),
+        local_name!("marquee") => make!(HTMLElement),
+        local_name!("menu") => make!(HTMLMenuElement),
+        local_name!("meta") => make!(HTMLMetaElement),
+        local_name!("meter") => make!(HTMLMeterElement),
         // https://html.spec.whatwg.org/multipage/#other-elements,-attributes-and-apis:multicol
-        local_name!("multicol")   => make!(HTMLUnknownElement),
-        local_name!("nav")        => make!(HTMLElement),
+        local_name!("multicol") => make!(HTMLUnknownElement),
+        local_name!("nav") => make!(HTMLElement),
         // https://html.spec.whatwg.org/multipage/#other-elements,-attributes-and-apis:nextid
-        local_name!("nextid")     => make!(HTMLUnknownElement),
-        local_name!("nobr")       => make!(HTMLElement),
-        local_name!("noframes")   => make!(HTMLElement),
-        local_name!("noscript")   => make!(HTMLElement),
-        local_name!("object")     => make!(HTMLObjectElement),
-        local_name!("ol")         => make!(HTMLOListElement),
-        local_name!("optgroup")   => make!(HTMLOptGroupElement),
-        local_name!("option")     => make!(HTMLOptionElement),
-        local_name!("output")     => make!(HTMLOutputElement),
-        local_name!("p")          => make!(HTMLParagraphElement),
-        local_name!("param")      => make!(HTMLParamElement),
-        local_name!("plaintext")  => make!(HTMLPreElement),
-        local_name!("pre")        => make!(HTMLPreElement),
-        local_name!("progress")   => make!(HTMLProgressElement),
-        local_name!("q")          => make!(HTMLQuoteElement),
-        local_name!("rp")         => make!(HTMLElement),
-        local_name!("rt")         => make!(HTMLElement),
-        local_name!("ruby")       => make!(HTMLElement),
-        local_name!("s")          => make!(HTMLElement),
-        local_name!("samp")       => make!(HTMLElement),
-        local_name!("script")     => make!(HTMLScriptElement, creator),
-        local_name!("section")    => make!(HTMLElement),
-        local_name!("select")     => make!(HTMLSelectElement),
-        local_name!("small")      => make!(HTMLElement),
-        local_name!("source")     => make!(HTMLSourceElement),
+        local_name!("nextid") => make!(HTMLUnknownElement),
+        local_name!("nobr") => make!(HTMLElement),
+        local_name!("noframes") => make!(HTMLElement),
+        local_name!("noscript") => make!(HTMLElement),
+        local_name!("object") => make!(HTMLObjectElement),
+        local_name!("ol") => make!(HTMLOListElement),
+        local_name!("optgroup") => make!(HTMLOptGroupElement),
+        local_name!("option") => make!(HTMLOptionElement),
+        local_name!("output") => make!(HTMLOutputElement),
+        local_name!("p") => make!(HTMLParagraphElement),
+        local_name!("param") => make!(HTMLParamElement),
+        local_name!("picture") => make!(HTMLPictureElement),
+        local_name!("plaintext") => make!(HTMLPreElement),
+        local_name!("pre") => make!(HTMLPreElement),
+        local_name!("progress") => make!(HTMLProgressElement),
+        local_name!("q") => make!(HTMLQuoteElement),
+        local_name!("rp") => make!(HTMLElement),
+        local_name!("rt") => make!(HTMLElement),
+        local_name!("ruby") => make!(HTMLElement),
+        local_name!("s") => make!(HTMLElement),
+        local_name!("samp") => make!(HTMLElement),
+        local_name!("script") => make!(HTMLScriptElement, creator),
+        local_name!("section") => make!(HTMLElement),
+        local_name!("select") => make!(HTMLSelectElement),
+        local_name!("small") => make!(HTMLElement),
+        local_name!("source") => make!(HTMLSourceElement),
         // https://html.spec.whatwg.org/multipage/#other-elements,-attributes-and-apis:spacer
-        local_name!("spacer")     => make!(HTMLUnknownElement),
-        local_name!("span")       => make!(HTMLSpanElement),
-        local_name!("strike")     => make!(HTMLElement),
-        local_name!("strong")     => make!(HTMLElement),
-        local_name!("style")      => make!(HTMLStyleElement, creator),
-        local_name!("sub")        => make!(HTMLElement),
-        local_name!("summary")    => make!(HTMLElement),
-        local_name!("sup")        => make!(HTMLElement),
-        local_name!("table")      => make!(HTMLTableElement),
-        local_name!("tbody")      => make!(HTMLTableSectionElement),
-        local_name!("td")         => make!(HTMLTableDataCellElement),
-        local_name!("template")   => make!(HTMLTemplateElement),
-        local_name!("textarea")   => make!(HTMLTextAreaElement),
+        local_name!("spacer") => make!(HTMLUnknownElement),
+        local_name!("span") => make!(HTMLSpanElement),
+        local_name!("strike") => make!(HTMLElement),
+        local_name!("strong") => make!(HTMLElement),
+        local_name!("style") => make!(HTMLStyleElement, creator),
+        local_name!("sub") => make!(HTMLElement),
+        local_name!("summary") => make!(HTMLElement),
+        local_name!("sup") => make!(HTMLElement),
+        local_name!("table") => make!(HTMLTableElement),
+        local_name!("tbody") => make!(HTMLTableSectionElement),
+        local_name!("td") => make!(HTMLTableCellElement),
+        local_name!("template") => make!(HTMLTemplateElement),
+        local_name!("textarea") => make!(HTMLTextAreaElement),
         // https://html.spec.whatwg.org/multipage/#the-tfoot-element:concept-element-dom
-        local_name!("tfoot")      => make!(HTMLTableSectionElement),
-        local_name!("th")         => make!(HTMLTableHeaderCellElement),
+        local_name!("tfoot") => make!(HTMLTableSectionElement),
+        local_name!("th") => make!(HTMLTableCellElement),
         // https://html.spec.whatwg.org/multipage/#the-thead-element:concept-element-dom
-        local_name!("thead")      => make!(HTMLTableSectionElement),
-        local_name!("time")       => make!(HTMLTimeElement),
-        local_name!("title")      => make!(HTMLTitleElement),
-        local_name!("tr")         => make!(HTMLTableRowElement),
-        local_name!("tt")         => make!(HTMLElement),
-        local_name!("track")      => make!(HTMLTrackElement),
-        local_name!("u")          => make!(HTMLElement),
-        local_name!("ul")         => make!(HTMLUListElement),
-        local_name!("var")        => make!(HTMLElement),
-        local_name!("video")      => make!(HTMLVideoElement),
-        local_name!("wbr")        => make!(HTMLElement),
-        local_name!("xmp")        => make!(HTMLPreElement),
-        _                   => make!(HTMLUnknownElement),
+        local_name!("thead") => make!(HTMLTableSectionElement),
+        local_name!("time") => make!(HTMLTimeElement),
+        local_name!("title") => make!(HTMLTitleElement),
+        local_name!("tr") => make!(HTMLTableRowElement),
+        local_name!("tt") => make!(HTMLElement),
+        local_name!("track") => make!(HTMLTrackElement),
+        local_name!("u") => make!(HTMLElement),
+        local_name!("ul") => make!(HTMLUListElement),
+        local_name!("var") => make!(HTMLElement),
+        local_name!("video") => make!(HTMLVideoElement),
+        local_name!("wbr") => make!(HTMLElement),
+        local_name!("xmp") => make!(HTMLPreElement),
+        _ if is_valid_custom_element_name(&*name.local) => make!(HTMLElement),
+        _ => make!(HTMLUnknownElement),
     }
 }
 
-pub fn create_element(name: QualName,
-                      prefix: Option<Prefix>,
-                      document: &Document,
-                      creator: ElementCreator)
-                      -> Root<Element> {
-    // FIXME(ajeffrey): Convert directly from Prefix to DOMString.
-
-    let prefix = prefix.map(|p| DOMString::from(&*p));
-
+pub fn create_element(
+    name: QualName,
+    is: Option<LocalName>,
+    document: &Document,
+    creator: ElementCreator,
+    mode: CustomElementCreationMode,
+) -> DomRoot<Element> {
+    let prefix = name.prefix.clone();
     match name.ns {
-        ns!(html)   => create_html_element(name, prefix, document, creator),
-        ns!(svg)    => create_svg_element(name, prefix, document),
-        _           => Element::new(name.local, name.ns, prefix, document)
+        ns!(html) => create_html_element(name, prefix, is, document, creator, mode),
+        ns!(svg) => create_svg_element(name, prefix, document),
+        _ => Element::new(name.local, name.ns, prefix, document),
     }
 }