Make struct part of unrooted_must_root handle type parameters

components/script/dom/browsercontext.rs

@@ -30,6 +30,7 @@ use std::default::Default;
 #[derive(JSTraceable)]
 #[privatize]
 #[allow(raw_pointer_derive)]
+#[must_root]
 pub struct BrowsingContext {
     history: Vec<SessionHistoryEntry>,
     active_index: usize,

components/script/page.rs

@@ -14,6 +14,7 @@ use std::rc::Rc;
 
 /// Encapsulates a handle to a frame in a frame tree.
 #[derive(JSTraceable)]
+#[allow(unrooted_must_root)] // FIXME(#6686) this is wrong
 pub struct Page {
     /// Pipeline id associated with this page.
     id: PipelineId,

components/script/script_task.rs

@@ -287,6 +287,8 @@ impl Drop for StackRootTLS {
 /// Information for an entire page. Pages are top-level browsing contexts and can contain multiple
 /// frames.
 #[derive(JSTraceable)]
+// ScriptTask instances are rooted on creation, so this is okay
+#[allow(unrooted_must_root)]
 pub struct ScriptTask {
     /// A handle to the information pertaining to page layout
     page: DOMRefCell<Option<Rc<Page>>>,