Auto merge of #16096 - stshine:die-modify-style-die, r=emilio

Use Servo-specific pseudo elements for anonymous box and text

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Use some fake pseudo elements to style servo-specific boxes in servo. Also, Since for nested inline elements non-inheritable properties are properly stored in the inline context of an inline fragment, so get
rid of them on the style using empty pseudo to do cascading.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #5625 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because refactoring

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components/script/layout_wrapper.rs

@@ -788,16 +788,7 @@ impl<'ln> ThreadSafeLayoutNode for ServoThreadSafeLayoutNode<'ln> {
         self.node.type_id()
     }
 
-    fn style_for_text_node(&self) -> Arc<ComputedValues> {
-        // Text nodes get a copy of the parent style. Inheriting all non-
-        // inherited properties into the text node is odd from a CSS
-        // perspective, but makes fragment construction easier (by making
-        // properties like vertical-align on fragments have values that
-        // match the parent element). This is an implementation detail of
-        // Servo layout that is not central to how fragment construction
-        // works, but would be difficult to change. (Text node style is
-        // also not visible to script.)
-        debug_assert!(self.is_text_node());
+    fn parent_style(&self) -> Arc<ComputedValues> {
         let parent = self.node.parent_node().unwrap().as_element().unwrap();
         let parent_data = parent.get_data().unwrap().borrow();
         parent_data.styles().primary.values().clone()