Reuse StylesheetContent for inline style sheets with identical content (#38540)

For duplicate style sheets with identical content, `StylesheetContents`
can be reused to avoid redundant parsing of the inline style sheets.
Since duplicate stylesheets is a common case with web components, this
change will significantly improve performance. Additionally, the cache
hit rate of stylo's `CascadeDataCache` can now be significantly
improved.

When shared `StylesheetContents` is modified, copy-on-write will occur
to avoid affecting other sharers. And then updates the references to
`CssRule` or `PropertyDeclarationBlock` stored in the CSSOMs to ensure
that modifications are made only on the new copy.

Signed-off-by: sharpshooter_pt <ibluegalaxy_taoj@163.com>

components/script/dom/medialist.rs

@@ -2,6 +2,8 @@
  * 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 cssparser::{Parser, ParserInput};
 use dom_struct::dom_struct;
 use servo_arc::Arc;
@@ -26,7 +28,7 @@ pub(crate) struct MediaList {
     parent_stylesheet: Dom<CSSStyleSheet>,
     #[ignore_malloc_size_of = "Arc"]
     #[no_trace]
-    media_queries: Arc<Locked<StyleMediaList>>,
+    media_queries: RefCell<Arc<Locked<StyleMediaList>>>,
 }
 
 impl MediaList {
@@ -38,7 +40,7 @@ impl MediaList {
         MediaList {
             parent_stylesheet: Dom::from_ref(parent_stylesheet),
             reflector_: Reflector::new(),
-            media_queries,
+            media_queries: RefCell::new(media_queries),
         }
     }
 
@@ -57,7 +59,7 @@ impl MediaList {
     }
 
     fn shared_lock(&self) -> &SharedRwLock {
-        &self.parent_stylesheet.style_stylesheet().shared_lock
+        self.parent_stylesheet.shared_lock()
     }
 
     /// <https://drafts.csswg.org/cssom/#parse-a-media-query-list>
@@ -109,7 +111,11 @@ impl MediaList {
 
     pub(crate) fn clone_media_list(&self) -> StyleMediaList {
         let guard = self.shared_lock().read();
-        self.media_queries.read_with(&guard).clone()
+        self.media_queries.borrow().read_with(&guard).clone()
+    }
+
+    pub(crate) fn update_media_list(&self, media_queries: Arc<Locked<StyleMediaList>>) {
+        *self.media_queries.borrow_mut() = media_queries;
     }
 }
 
@@ -117,14 +123,21 @@ impl MediaListMethods<crate::DomTypeHolder> for MediaList {
     /// <https://drafts.csswg.org/cssom/#dom-medialist-mediatext>
     fn MediaText(&self) -> DOMString {
         let guard = self.shared_lock().read();
-        DOMString::from(self.media_queries.read_with(&guard).to_css_string())
+        DOMString::from(
+            self.media_queries
+                .borrow()
+                .read_with(&guard)
+                .to_css_string(),
+        )
     }
 
     /// <https://drafts.csswg.org/cssom/#dom-medialist-mediatext>
     fn SetMediaText(&self, value: DOMString) {
+        self.parent_stylesheet.will_modify();
         let global = self.global();
         let mut guard = self.shared_lock().write();
-        let media_queries = self.media_queries.write_with(&mut guard);
+        let media_queries_borrowed = self.media_queries.borrow();
+        let media_queries = media_queries_borrowed.write_with(&mut guard);
         *media_queries = Self::parse_media_list(&value, global.as_window());
         self.parent_stylesheet.notify_invalidations();
     }
@@ -132,13 +145,18 @@ impl MediaListMethods<crate::DomTypeHolder> for MediaList {
     // https://drafts.csswg.org/cssom/#dom-medialist-length
     fn Length(&self) -> u32 {
         let guard = self.shared_lock().read();
-        self.media_queries.read_with(&guard).media_queries.len() as u32
+        self.media_queries
+            .borrow()
+            .read_with(&guard)
+            .media_queries
+            .len() as u32
     }
 
     /// <https://drafts.csswg.org/cssom/#dom-medialist-item>
     fn Item(&self, index: u32) -> Option<DOMString> {
         let guard = self.shared_lock().read();
         self.media_queries
+            .borrow()
             .read_with(&guard)
             .media_queries
             .get(index as usize)
@@ -160,18 +178,28 @@ impl MediaListMethods<crate::DomTypeHolder> for MediaList {
             return;
         }
         // Step 3
-        let m_serialized = m.clone().unwrap().to_css_string();
-        let mut guard = self.shared_lock().write();
-        let mq = self.media_queries.write_with(&mut guard);
-        let any = mq
-            .media_queries
-            .iter()
-            .any(|q| m_serialized == q.to_css_string());
-        if any {
-            return;
+        {
+            let m_serialized = m.clone().unwrap().to_css_string();
+            let guard = self.shared_lock().read();
+            let any = self
+                .media_queries
+                .borrow()
+                .read_with(&guard)
+                .media_queries
+                .iter()
+                .any(|q| m_serialized == q.to_css_string());
+            if any {
+                return;
+            }
         }
         // Step 4
-        mq.media_queries.push(m.unwrap());
+        self.parent_stylesheet.will_modify();
+        let mut guard = self.shared_lock().write();
+        self.media_queries
+            .borrow()
+            .write_with(&mut guard)
+            .media_queries
+            .push(m.unwrap());
         self.parent_stylesheet.notify_invalidations();
     }
 
@@ -185,9 +213,11 @@ impl MediaListMethods<crate::DomTypeHolder> for MediaList {
             return;
         }
         // Step 3
+        self.parent_stylesheet.will_modify();
         let m_serialized = m.unwrap().to_css_string();
         let mut guard = self.shared_lock().write();
-        let media_list = self.media_queries.write_with(&mut guard);
+        let media_queries_borrowed = self.media_queries.borrow();
+        let media_list = media_queries_borrowed.write_with(&mut guard);
         let new_vec = media_list
             .media_queries
             .drain(..)