Only allow UA widgets as children of media elements

Do not allow pseudo-elements for replaced elements

components/layout/construct.rs

@@ -705,11 +705,16 @@ impl<'a, ConcreteThreadSafeLayoutNode: ThreadSafeLayoutNode>
         // List of absolute descendants, in tree order.
         let mut abs_descendants = AbsoluteDescendants::new();
         let mut legalizer = Legalizer::new();
-        if !node.is_replaced_content() ||
-            node.type_id() == Some(LayoutNodeType::Element(LayoutElementType::HTMLMediaElement))
-        {
+        let is_media_element_with_widget = node.type_id() ==
+            Some(LayoutNodeType::Element(LayoutElementType::HTMLMediaElement)) &&
+            node.as_element().unwrap().is_shadow_host();
+        if !node.is_replaced_content() || is_media_element_with_widget {
             for kid in node.children() {
                 if kid.get_pseudo_element_type() != PseudoElementType::Normal {
+                    if node.is_replaced_content() {
+                        // Replaced elements don't have pseudo-elements per spec.
+                        continue;
+                    }
                     self.process(&kid);
                 }
 

components/layout_thread/dom_wrapper.rs

@@ -1397,6 +1397,10 @@ impl<'le> ThreadSafeLayoutElement for ServoThreadSafeLayoutElement<'le> {
             .expect("Unstyled layout node?")
             .borrow()
     }
+
+    fn is_shadow_host(&self) -> bool {
+        self.element.shadow_root().is_some()
+    }
 }
 
 /// This implementation of `::selectors::Element` is used for implementing lazy

components/script/dom/document.rs

@@ -4581,6 +4581,7 @@ impl DocumentMethods for Document {
         self.exit_fullscreen()
     }
 
+    // check-tidy: no specs after this line
     // Servo only API to get an instance of the controls of a specific
     // media element matching the given id.
     fn ServoGetMediaControls(&self, id: DOMString) -> Fallible<DomRoot<ShadowRoot>> {

components/script/dom/shadowroot.rs

@@ -46,8 +46,6 @@ pub struct ShadowRoot {
     author_styles: DomRefCell<AuthorStyles<StyleSheetInDocument>>,
     stylesheet_list: MutNullableDom<StyleSheetList>,
     window: Dom<Window>,
-    /// Whether this ShadowRoot hosts a User Agent widget.
-    is_widget: IsUserAgentWidget,
 }
 
 impl ShadowRoot {
@@ -72,7 +70,6 @@ impl ShadowRoot {
             author_styles: DomRefCell::new(AuthorStyles::new()),
             stylesheet_list: MutNullableDom::new(None),
             window: Dom::from_ref(document.window()),
-            is_widget,
         }
     }
 
@@ -170,10 +167,6 @@ impl ShadowRoot {
             root,
         );
     }
-
-    pub fn is_user_agent_widget(&self) -> bool {
-        self.is_widget == IsUserAgentWidget::Yes
-    }
 }
 
 impl ShadowRootMethods for ShadowRoot {

components/script_layout_interface/wrapper_traits.rs

@@ -490,4 +490,6 @@ pub trait ThreadSafeLayoutElement:
                 .clone(),
         }
     }
+
+    fn is_shadow_host(&self) -> bool;
 }

ports/glutin/resources.rs

@@ -28,7 +28,7 @@ fn filename(file: Resource) -> &'static str {
         Resource::ServoCSS => "servo.css",
         Resource::PresentationalHintsCSS => "presentational-hints.css",
         Resource::QuirksModeCSS => "quirks-mode.css",
-        Resource::RippyPNG => "rippy.png", 
+        Resource::RippyPNG => "rippy.png",
         Resource::MediaControlsCSS => "media_controls.css",
         Resource::MediaControlsJS => "media_controls.js",
     }