Auto merge of #14930 - zaynetro:remove-stylesheets, r=emilio

Implement support for removing stylesheets from their document

<!-- Please describe your changes on the following line: -->
This pull request implements removing styles from the document when

* `<link>` element with associated styles is removed
* `<style>` element is removed

Additionally, it tests that when `<style>` element is changed. Styles are being reapplied correctly.

---
<!-- 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 #14886 (github issue number if applicable).

<!-- Either: -->
- [x] There are tests for these changes

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

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components/script/dom/htmllinkelement.rs

@@ -18,7 +18,7 @@ use dom::element::{AttributeMutation, Element, ElementCreator};
 use dom::element::{cors_setting_for_element, reflect_cross_origin_attribute, set_cross_origin_attribute};
 use dom::globalscope::GlobalScope;
 use dom::htmlelement::HTMLElement;
-use dom::node::{Node, document_from_node, window_from_node};
+use dom::node::{Node, UnbindContext, document_from_node, window_from_node};
 use dom::stylesheet::StyleSheet as DOMStyleSheet;
 use dom::virtualmethods::VirtualMethods;
 use html5ever_atoms::LocalName;
@@ -228,6 +228,15 @@ impl VirtualMethods for HTMLLinkElement {
             }
         }
     }
+
+    fn unbind_from_tree(&self, context: &UnbindContext) {
+        if let Some(ref s) = self.super_type() {
+            s.unbind_from_tree(context);
+        }
+
+        let document = document_from_node(self);
+        document.invalidate_stylesheets();
+    }
 }
 
 

components/script/dom/htmlstyleelement.rs

@@ -15,7 +15,7 @@ use dom::document::Document;
 use dom::element::{Element, ElementCreator};
 use dom::eventtarget::EventTarget;
 use dom::htmlelement::HTMLElement;
-use dom::node::{ChildrenMutation, Node, document_from_node, window_from_node};
+use dom::node::{ChildrenMutation, Node, UnbindContext, document_from_node, window_from_node};
 use dom::stylesheet::StyleSheet as DOMStyleSheet;
 use dom::virtualmethods::VirtualMethods;
 use html5ever_atoms::LocalName;
@@ -161,6 +161,15 @@ impl VirtualMethods for HTMLStyleElement {
             self.parse_own_css();
         }
     }
+
+    fn unbind_from_tree(&self, context: &UnbindContext) {
+        if let Some(ref s) = self.super_type() {
+            s.unbind_from_tree(context);
+        }
+
+        let doc = document_from_node(self);
+        doc.invalidate_stylesheets();
+    }
 }
 
 impl StylesheetOwner for HTMLStyleElement {