script: Move CSS DOM interfaces to script/dom/css/ (#40241)

Moves interfaces defined by the CSS spec to the `script/dom/css/` module
from `script/dom/`.

Testing: Just a refactor shouldn't need any testing
Fixes: Partially #38901

Signed-off-by: WaterWhisperer <waterwhisperer24@qq.com>

components/script/dom/css/cssimportrule.rs

@@ -0,0 +1,86 @@
+/* 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 https://mozilla.org/MPL/2.0/. */
+
+use std::cell::RefCell;
+
+use dom_struct::dom_struct;
+use servo_arc::Arc;
+use style::shared_lock::{Locked, ToCssWithGuard};
+use style::stylesheets::import_rule::ImportLayer;
+use style::stylesheets::{CssRuleType, ImportRule};
+use style_traits::ToCss;
+
+use super::cssrule::{CSSRule, SpecificCSSRule};
+use super::cssstylesheet::CSSStyleSheet;
+use crate::dom::bindings::codegen::Bindings::CSSImportRuleBinding::CSSImportRuleMethods;
+use crate::dom::bindings::reflector::reflect_dom_object;
+use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::str::DOMString;
+use crate::dom::window::Window;
+use crate::script_runtime::CanGc;
+
+#[dom_struct]
+pub(crate) struct CSSImportRule {
+    cssrule: CSSRule,
+    #[ignore_malloc_size_of = "Stylo"]
+    #[no_trace]
+    import_rule: RefCell<Arc<Locked<ImportRule>>>,
+}
+
+impl CSSImportRule {
+    fn new_inherited(
+        parent_stylesheet: &CSSStyleSheet,
+        import_rule: Arc<Locked<ImportRule>>,
+    ) -> Self {
+        CSSImportRule {
+            cssrule: CSSRule::new_inherited(parent_stylesheet),
+            import_rule: RefCell::new(import_rule),
+        }
+    }
+
+    #[cfg_attr(crown, allow(crown::unrooted_must_root))]
+    pub(crate) fn new(
+        window: &Window,
+        parent_stylesheet: &CSSStyleSheet,
+        import_rule: Arc<Locked<ImportRule>>,
+        can_gc: CanGc,
+    ) -> DomRoot<Self> {
+        reflect_dom_object(
+            Box::new(Self::new_inherited(parent_stylesheet, import_rule)),
+            window,
+            can_gc,
+        )
+    }
+
+    pub(crate) fn update_rule(&self, import_rule: Arc<Locked<ImportRule>>) {
+        *self.import_rule.borrow_mut() = import_rule;
+    }
+}
+
+impl SpecificCSSRule for CSSImportRule {
+    fn ty(&self) -> CssRuleType {
+        CssRuleType::Import
+    }
+
+    fn get_css(&self) -> DOMString {
+        let guard = self.cssrule.shared_lock().read();
+        self.import_rule
+            .borrow()
+            .read_with(&guard)
+            .to_css_string(&guard)
+            .into()
+    }
+}
+
+impl CSSImportRuleMethods<crate::DomTypeHolder> for CSSImportRule {
+    /// <https://drafts.csswg.org/cssom-1/#dom-cssimportrule-layername>
+    fn GetLayerName(&self) -> Option<DOMString> {
+        let guard = self.cssrule.shared_lock().read();
+        match &self.import_rule.borrow().read_with(&guard).layer {
+            ImportLayer::None => None,
+            ImportLayer::Anonymous => Some(DOMString::new()),
+            ImportLayer::Named(name) => Some(DOMString::from_string(name.to_css_string())),
+        }
+    }
+}