layout: Add support for table rows, columns, rowgroups and colgroups (#31341)

This adds support for table rows, columns, rowgroups and colgroups.
There are few additions here:

1. The createion of fragments, which allows script queries and hit
   testing to work properly. These fragments are empty as all cells are
   still direct descendants of the table fragment.
2. Properly handling size information from tracks and track groups as
   well as frustrating rules about reordering rowgroups.
3. Painting a background seemlessly across track groups and groups. This
   is a thing that isn't done in legacy layout (nor WebKit)!

Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/script/dom/htmltablecolelement.rs

@@ -3,14 +3,23 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use dom_struct::dom_struct;
-use html5ever::{LocalName, Prefix};
+use html5ever::{local_name, namespace_url, ns, LocalName, Prefix};
 use js::rust::HandleObject;
+use style::attr::AttrValue;
 
+use super::bindings::root::LayoutDom;
+use super::element::Element;
+use crate::dom::bindings::codegen::Bindings::HTMLTableColElementBinding::HTMLTableColElementMethods;
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::str::DOMString;
 use crate::dom::document::Document;
+use crate::dom::element::LayoutElementHelpers;
 use crate::dom::htmlelement::HTMLElement;
 use crate::dom::node::Node;
+use crate::dom::virtualmethods::VirtualMethods;
+
+const DEFAULT_SPAN: u32 = 1;
 
 #[dom_struct]
 pub struct HTMLTableColElement {
@@ -47,3 +56,46 @@ impl HTMLTableColElement {
         n
     }
 }
+
+impl HTMLTableColElementMethods for HTMLTableColElement {
+    // <https://html.spec.whatwg.org/multipage/#attr-col-span>
+    make_uint_getter!(Span, "span", DEFAULT_SPAN);
+    // <https://html.spec.whatwg.org/multipage/#attr-col-span>
+    make_uint_setter!(SetSpan, "span", DEFAULT_SPAN);
+}
+
+pub trait HTMLTableColElementLayoutHelpers<'dom> {
+    fn get_span(self) -> Option<u32>;
+}
+
+impl<'dom> HTMLTableColElementLayoutHelpers<'dom> for LayoutDom<'dom, HTMLTableColElement> {
+    fn get_span(self) -> Option<u32> {
+        self.upcast::<Element>()
+            .get_attr_for_layout(&ns!(), &local_name!("span"))
+            .map(AttrValue::as_uint)
+    }
+}
+
+impl VirtualMethods for HTMLTableColElement {
+    fn super_type(&self) -> Option<&dyn VirtualMethods> {
+        Some(self.upcast::<HTMLElement>() as &dyn VirtualMethods)
+    }
+
+    fn parse_plain_attribute(&self, local_name: &LocalName, value: DOMString) -> AttrValue {
+        match *local_name {
+            local_name!("span") => {
+                let mut attr = AttrValue::from_u32(value.into(), DEFAULT_SPAN);
+                if let AttrValue::UInt(_, ref mut val) = attr {
+                    if *val == 0 {
+                        *val = 1;
+                    }
+                }
+                attr
+            },
+            _ => self
+                .super_type()
+                .unwrap()
+                .parse_plain_attribute(local_name, value),
+        }
+    }
+}